Without a doubt, history was the subject Rodrigo liked the least. Maybe it wasn't the fault of the subject itself, but the way the Mole taught the class. Every day he would sit in his armchair, put on his tiny, round glasses and take out an enormous book from his briefcase before reading page after page to them. Every day was the same. That's why Rodrigo and all his classmates were left open-mouthed when, one day, the Mole entered the classroom and, instead of sitting in his armchair and putting on his tiny glasses, he remained standing in front of the class and announced that he would be taking them on a trip to a medieval castle. As if that wasn't enough of a surprise, the Mole then began to explain to them that they would be spending three full days in the castle, eating in the armoury and sleeping in the old chambers of the nobles.

In the four months that Rodrigo had been at the School of San Claudio, many teachers had taken them on a trip but they had never spent the night outside of the boarding school. Perhaps the Mole wanted to make up for the endless hours of boredom he had inflicted on them? That was what he had thought, but when they arrived at the castle he realised he was wrong. The guide's explanations were just as monotonous as those of the Mole.

'Now, if you'll follow me through this corridor we'll come out into the courtyard where I will show you a very special tower,' said the gangling, bald man who was showing them the castle. When he saw the group moving forward, Rodrigo quickly abandoned his daydreaming. Resigned, he turned his gaze away from the large window and began to walk with the rest of his classmates until he heard a voice whisper behind him.

'Hey, Rodri. Can you give me a hand?'

Turning round, he saw his friend, Oliver, standing in front of one of the suits of armour that decorated the room. He had a mischievous glint in his eyes.

'Come on, we're going to get left behind,' Rodrigo said when he saw their classmates beginning to move further away.

'That's what I want!' Oliver whispered. 'I'm going to put this suit of armour on and then I'll run up behind them and scare them.'

'Yeah, sure,' Rodrigo replied. 'It'll be very funny, but I reckon this would be your last trip this year.'

'You think I'd get into trouble?'

'I'm absolutely certain.'

'Now that you say it, maybe you're right. I'll save the jokes for the end of year trip. After all, they can't punish me during the holidays, right?'

Rodrigo smiled and nodded his head. Oliver was his best friend at the boarding school, despite the two of them being very different. He was always up to no good, breaking all the rules and continuously being disciplined in some way or another. Rodrigo tried to stop Oliver from carrying out his more ridiculous ideas, and he sometimes managed it. Nobody knew exactly how the two of them had become such firm friends. Even Rodrigo himself didn't understand fully how it happened, although it was surely because they had one thing in common: the two of them were new students at the boarding school, having arrived there after spending their lives moving from one place to another.

In Rodrigo's case, this constant coming and going was due to the continual job changes of his father, forcing them to move from one city to another (his mother had died when he was very young). Oliver, however, had passed through five different schools in his parents' desperate attempt to find one that could straighten him out.

In every other aspect, Rodrigo and Oliver weren't at all alike. Even their appearance couldn't be more different: Oliver was the tallest in the school, given that he was repeating the last year of primary education; not only was Rodrigo a year younger, he was also small for his age. The result was that the two of them together were unmistakeable: one tall boy with forever messy black hair and another with smooth, brown hair who scarcely reached his friend's shoulders.

'Come on, before the Mole comes looking for us,' said Rodrigo, seeing that they were now alone in the room.

The two of them began walking quickly after the rest of their classmates who had begun descending a steep, spiral staircase. When they finally reached the Mole, he stared at them before moving behind them. He probably already suspected that Oliver was plotting another of his tricks.

After descending an endless succession of slippery steps, they finally reached the exterior of the castle where they crossed a stone courtyard before reaching the foot of a solitary tower. Its stone walls stretched much higher into the sky than the rest of the castle, however, it was so narrow that it seemed more like a thick column than a tower.

'Welcome to the Tower of Torment,' the guide said when the students had gathered round. 'It was given its name when Count Zacara, the lord of the castle, ordered its construction to torment his enemies and the slaves who disobeyed him.'

Small laughs and whispers fluttered through the group and Rodrigo knew exactly why.

'What's so funny?' asked the guide with surprise.

'Zacara is Rodrigo's surname,' Oliver explained, leaning his arm on Rodrigo's shoulder.

'Well, you must be a descendant of the count,' said the guide, gazing at him with curiosity. 'He was the first person to have that surname. It comes from the ancient city of Zacara, with this castle remaining as the only testament to the place.'

Rodrigo's classmates began to make jokes, bowing before him and saying things like "at your service, lord Count," "mercy, please don't throw me in the tower, lord Count." Suddenly, he wished he had a more common surname, like Perez or Garcia. Oliver must have realised what he'd done because he quickly approached Rodrigo and said quietly,

'I'm sorry. I think I've put my foot in it. Why can I never keep my mouth shut?'

'Don't worry,' Rodrigo said. 'If you hadn't said it, somebody else would have.'

'Anyway, as I was saying,' the guide continued. 'When the count locked someone in this tower, he would order the door to be bricked up with stone and cement and he would condemn the person to die of thirst and hunger.'

'Hey, Rodrigo, I hope you haven't inherited a bad gene from your great-great-great-great-grandfather,' joked Guillermo, an idiot who thought he was extremely funny.

'You're worse. You've inherited a monkey's face from a Neanderthal,' Oliver replied, drawing laughs from the others. Fortunately, Oliver always had a funny response for anyone trying to be too clever.

'Right, that's enough!' the guide interrupted. He was beginning to get anxious. 'As you can see, escaping from this tower would appear completely impossible. The door was bricked up and the only way air enters is through those small holes you can see at the top. Barely an arm can get through them.'

'Why did they make air holes if the count wanted to leave the prisoners to die?' Oliver asked.

'It was surely to make them die slower and to prolong their suffering,' the guide answered. 'In any case, it was impossible for anyone to escape through those holes and they certainly couldn't leave through the door. However, legend tells us that two prisoners in this tower managed to escape without leaving a trace.'

With the silence that followed his words, the guide understood for the first time that he had captured the attention of his audience so he began explaining the legend.

'The first prisoner to escape was one of the count's soldiers who was accused of treason. They locked him in the tower and sealed the door but a month later, when they went to find his remains so he could be buried, they found absolutely nothing. Not even clothing. Twelve years later Count Zacara himself was a prisoner. The city's inhabitants, who had had enough of his injustices and taxes, rebelled against him and threw him in his own tower. However, once again, nothing was found when they entered the tower to remove his remains. Nobody ever knew how he managed to escape but the tower was never used to lock anyone away again.'

'It must have a secret exit,' Oliver said, seeming interested in the guide's explanations for the first time. 'Can we go up to the top?'

'It's too late for that,' the man replied. 'It's getting dark and inside the tower the only light comes from what enters through the walls' tiny holes.'

'But the sun's still up!' Oliver replied.

'I know, but the tower has 350 steps so we would take a while to reach the top. Night will have fallen before we come back down.'

'What about tomorrow?' the boy insisted.

'Perhaps,' the guide smiled as if he had guessed what Oliver was thinking. 'But don't get your hopes up. Many investigators have searched the tower centimetre by centimetre and none have found a secret passageway.'

An hour later, Rodrigo still had the story of Count Zacara bouncing around his head.

'How can he be so sure that I'm a descendant of the count?' he asked his friends on their way down to the dining room. 'I can't be the only Zacara in the world, right?'

'Of course not,' Alvaro replied. 'But if the count was the first person to have that surname then any Zacara is one of his descendants.'

Alvaro was right, as always. It was all very strange. Rodrigo had always considered counts and nobles to be characters in films or, in the worst cases, history books. Count Zacara, on the other hand, was a relative of his.

'Hey, Rodri,' Oliver said, stopping suddenly. 'Did you know that if the count was locked in the tower before having children, you would never have existed?'

'Well, you don't know that,' Sergio replied. 'If it's true that the count escaped from the tower, he could have had children afterwards.'

Rodrigo remained quiet. He was lost in his own thoughts. Had his ancestor really been so cruel and merciless? Had he deserved a slave rebellion and being condemned to die in his own tower? He was embarrassed to think his surname came from a person like that.

'Do you think the tower has a secret passageway?' Oliver asked.

'I don't think so,' Sergio replied. 'If there was, the investigators would have found it. I reckon the count and the other prisoner managed to escape by digging a tunnel underneath the door.'

'I doubt it,' Rodrigo said. 'I'm sure there are metres of stone beneath the tower. A tower as high as that has to have good foundations to make sure it doesn't fall down.'

'That's why there must be a secret way out,' Oliver insisted. 'Something enabled them–'

'It's just a legend,' Rodrigo interrupted. 'People got bored easily in the Middle Ages and they invented stories to pass the time.'

Oliver opened his mouth to reply but at that moment the Mole appeared, asking for silence.

'When you've finished dinner, head to your rooms,' he said. 'You have one hour for chatting, reading or whatever you want to do, but come eleven o'clock everyone must be in bed. I don't want to hear anyone speak or see a single light on past this time. Of course, nobody should leave their room unless it is to use the bathroom and I don't want to see anyone in a room that is not theirs.'

This was the most eagerly anticipated moment of the day for Rodrigo and his friends. Although they were already used to sharing a room at boarding school, the short while they had free before going to sleep was always the best part of the day. After entering Oliver's room, Rodrigo took out his MP3 player and connected it to some small speakers. Seconds later, the music of Morenoise, his favourite band, began to play.

'Your MP3 player can record things, right?' Sergio asked.

'Of course,' Oliver replied. 'It can record up to ten hours without a break. Why do you ask?'

'Because I think we're in the perfect place to record electronic voice phenomena.'

'Electronic voice phe... what?'

'Electronic voice phenomena,' Sergio repeated seriously. 'It's a recording of the sounds of ghosts.'

Oliver stared at him and nodded his head, although he was obviously trying not to laugh.

'Great idea! We could interview them,' Oliver pressed a button on the MP3 player and moved it towards one of the window curtains. 'Good evening, sir. What should I call you? Ghost, phantom or lost soul?'

Rodrigo and Alvaro doubled over with laughter on the bed while Oliver continued his interview, feigning total seriousness.

'Tell me, how do you usually kill, sorry, I mean, pass the time? I understand that you like to open and close doors, turn lights on and off, move things around. Are there no videogames in the afterlife?'

Rodrigo had tears running down his face from laughing so much while Alvaro was punching the mattress. The only one who didn't seem to find it funny was Sergio.

'For your information,' he said, 'there are hundreds of electronic phenomena that have been recorded by famous investigators. They are almost always recorded in places where a terrible death has taken place. I bet loads of lost souls could be recorded in the Tower of Torment.'

'Yes, I imagine so,' Rodrigo said. His cheeks were starting to hurt from laughing so much. 'Giiiiive meeeeee sooouuuup. I'll give you anything for a plate of sooouuuuuuup.'

'You think you're funny? Well, if you're so sure that ghosts don't exist, you'll have no problem going up that tower and leaving the MP3 player recording all night. Let's see if you think the same tomorrow after listening to the recording.'

'I've got a problem,' Rodrigo said. 'Ghosts don't scare me, but the Mole does. If he finds us up at night, we'll be in deep trouble.'

'And I already have enough detention to last me to May,' Oliver added. 'If I have to start sacrificing my weekends in June, I want it to be for something that's really worth it.'

'Don't worry,' Sergio said, giving them a challenging smile. 'I'll take care of the Mole if he finds out.'

'Yeah, yeah,' Rodrigo replied. 'And how are you going to do that?'

'Can you see that gap above the rafter? It links to the bedroom next door. I've already checked.'

'Ok. So what?' Rodrigo said.

'Well, when we're all silent, I'll throw a stink bomb through the gap. There will be a huge racket and the Mole will have to go and see what's happening. You two will be able to go out without him knowing.'

'Not bad,' Oliver admitted, 'but I think there's a flaw in your plan, Sergio.'

'Where?'

'Well, we're not the ones who want to record ghosts. You do. We don't believe in ghosts.'

'You say you don't believe in ghosts but you're really just wimps.'

'Right, ok,' Oliver said. 'If it makes you happy, Rodrigo and I will take the MP3 player to the tower, we'll hide it and we'll leave it there to record all night. Tomorrow, we'll go and collect it and then we'll show you there's no such thing as ghosts.'

'Eh, don't include me in this,' Rodrigo said. He had absolutely no desire to head out into the night to climb that cursed tower. Simply thinking about it made the hairs on the back of his neck stand on end.

'Not so brave now?' Sergio teased.

'Your plan is nuts. What happens if the Mole enters our room and sees we're not here?'

'We'll say you went to the bathroom. Or better yet, we could put backpacks under your blankets. If he thinks we're all sleeping, he won't even turn on the light.'

'Great. And how are we going to get outside to the courtyard? You can't think we'll simply find the door open.'

'Of course not,' Oliver said this time, 'but it has a bolt that can be opened from the inside.'

'How do you know?' Rodrigo asked him.

'You have to pay attention to these things, Rodri. You never know when you'll have to escape from an insufferable history lesson!'

'Ok, ok. But I think you're forgetting the most important detail,' he replied, hoping to put an end to this foolish plan. 'We can't climb three hundred-odd stairs in the dark, and the guide said there is no light inside the tower.'

'Don't worry about that,' Oliver answered. 'I've brought a torch.'

Rodrigo tried to think of another objection to the plan but he was out of ideas. All he could do was sit there with his mouth open.

'Good. Everything's settled,' Oliver concluded. 'Sergio will throw a stink bomb into the bedroom next door and when the Mole appears to see what's happening, Rodri and I will escape. Then we'll go to the tower and leave the MP3 player somewhere hidden so it will record all night.'

'Excellent,' Sergio said. 'Then, when you come back, I'll throw another stink bomb so you can get back in again without the Mole finding you.'

'How will you know when we're on our way back?' Rodrigo asked.

'I can see the tower from here,' Sergio indicated, motioning to the window. 'When you get to the top, make signals with the torch through one of the holes in the wall. I'll calculate that it will take you the same amount of time to return. Then I'll throw the second stink bomb.'

'You won't need to,' Oliver said. 'We'll manage to get back in.'

'Of course he'll need to!' Rodrigo protested. 'The Mole is going to be watching the corridor. How do you think we're going to get back in without him seeing us?'

'I don't know. We'll think of something,' Oliver stammered.

'Well, I'd prefer it if Sergio threw another stink bomb just in case. We can't leave it to chance,' Rodrigo insisted, failing to understand the sudden stubbornness of his friend.

'Ok, ok, fine,' Oliver agreed, but for some reason he seemed worried as he did so.

Rodrigo almost wished that the Mole would find them and put an end to this stupid plan, even though that would mean some form of detention. However, the trick with the stink bomb worked surprisingly well: so well, in fact, that at quarter to midnight, he and Oliver were opening the huge castle gate. When they reached the stone courtyard, he still couldn't believe what they were doing but despite that, he walked quickly after Oliver with the freezing wind lashing at his face. Before he knew it, they had both reached the tower entrance. Suddenly, Oliver stopped.

'Why have you stopped?' Rodrigo asked him. He noticed that his friend was much paler than usual.

'I... I can't,' Oliver stuttered.

'What?'

'I can't go in there. I'm claustrophobic. I can't stand small spaces.'

'So what were you thinking when you got me mixed up in this?'

Rodrigo had to suppress the urge to give his friend a good slap.

'The truth is I hadn't thought about going up the tower. My plan was to hide it somewhere and record some ghostly voices on the MP3 player to mess with Sergio. Something like "Seeergiooooo, I'm coooomiiiiing for yoouuuu."'

'What a great idea!' Rodrigo said, relieved at the change of plan. 'Come on, we can hide it next to the wall.'

'Sergio's waiting for us to make signals with the torch from inside the tower. Now we have to go up. If we don't, he'll know and then he'll laugh at us.'

Suddenly, Rodrigo understood why Oliver had objected so much to the idea of the torch signals. His plan had never really been to go up to the top of the tower, but it had backfired on him.

'Come on, it's just a stone tower,' Rodrigo said, trying to encourage his friend, even though he himself wasn't keen to enter the tower.

'Ok, but I'll have to close my eyes as we go up so I can imagine I'm in a really big place. You'll have to guide me.'

'It's easy,' Rodrigo said, glancing at the winding, spiral staircase that lay before them. 'Just keep moving upwards and to the left. I assure you that you won't get lost. I'll go first and you can hold onto me.'

Oliver grasped Rodrigo's jacket and started to climb the stairs after him. It seemed like they were scaling a mountain rather than a staircase. The stairs were almost half a metre high and they made Rodrigo feel as though any slip or stumble would result in him rolling and falling to the very bottom. There was no handrail to hold onto, only the icy stone of the thick walls.

After a few endless minutes, Rodrigo was already breathless and his legs had begun to tremble.

'I'm going to rest a bit,' he said after a while. 'I'm out of breath.'

'We're more than halfway there,' Oliver encouraged. 'I'm counting the stairs. We've gone up two hundred and eight.'

Rodrigo sat on the step in front of him to regain his strength. He felt the cold, damp stone beneath his body. For a moment, he imagined what it would be like to be locked inside the tower with no hope of ever leaving. Just the thought made his body shudder so he tried to shake the thought from his mind. When he had got his breath back, he stood up and told Oliver they could continue. The sooner they reached the top, the sooner they could leave.

Two hundred and nine... Two hundred and ten... Rodrigo started to count the stairs too, hoping to distract his thoughts. When he reached two hundred and fifty, he told himself there were only a hundred more and he began to count backwards: ninety-nine, ninety-eight... His legs were becoming so tired that each step seemed like an insurmountable obstacle but he had no wish to stop again before reaching the top. Five, four, three, two, one...

When his foot finally reached the last step, Rodrigo shone the torch around their surroundings. They were in a small, round room with a high ceiling. He felt as though they were inside a tube. There were tiny holes in the stone walls you could barely fit a fist through, just like the guide had said. When he moved towards one of the gaps, he realised that Oliver was still gripping his jacket, his eyes closed.

'We made it, Oliver,' he said.

His friend opened his eyes but he closed them again straight away, panic written on his face. His breathing faltered as if he were about to choke at any moment.

'This is very small,' he said. 'I need to get out of here!'

'Calm down. I'm going to make signals with the torch. Then we'll hide the MP3 player and we'll get out of here.

Rodrigo started looking through the holes, searching for one that faced the castle. The holes were so narrow that it was like looking through the peephole of a door. Finally, he found one through which he could see the castle opposite them so he put the torch through the gap just as Oliver crashed into him and the torch slipped from his grasp, falling to the ground below.

'What are you doing?' Rodrigo shouted.

'Don't shout at me,' Oliver replied. 'If I stay still I get more nervous. Did I hurt you?'

'Worse than that! You made me drop the torch!'

'Don't worry. It can't have gone very far.'

Rodrigo heard his friend begin to move his hands around the floor, feeling for the torch.

'You don't understand! It fell outside the tower. We no longer have...'

Rodrigo couldn't finish his sentence. When he had turned round, he had seen something shining in the middle of the thick darkness that enveloped them. There were some words written on the stone wall giving off a faint blue light.

'Oliver,' he whispered. 'Open your eyes. You have to see this.'

'But didn't you say that we no longer have the torch?'

'Seriously, open your eyes, please.'

The curse that escaped from Oliver a second later served as confirmation that Rodrigo wasn't seeing things. Oliver could also see the shining words that had appeared on the wall. In fact, it was Oliver who moved towards them and began to read aloud:

The stars will fall from the sky

Before you can leave.

The moon will rise in the day

Before you can flee.

Rodrigo felt a chill run through his body. The words sounded like a threat. Although he knew that the tower door was open, he couldn't help but feel a terrible urge to get out of there.

'Do you think it's a puzzle?' Oliver asked him. Unlike Rodrigo, he seemed excited with the discovery: he had even forgotten about his claustrophobia. 'Could it be a clue to finding the secret passageway?'

'A puzzle? I think the meaning is very clear. It's a way of saying to the tower's prisoners that they'll never leave again. I, personally, would prefer not to spend another minute here.'

'But we have to hide the MP3 player,' Oliver objected.

'I don't care about the MP3 player!' Rodrigo answered, becoming more nervous by the minute. 'Anyway, we'll need it to reach the bottom. The screen has a bit of light at least. Come on. Follow me!'

Before his friend had time to object, Rodrigo headed for the narrow staircase, aided by the weak light emanating from the MP3 player, although he could scarcely see further than his own feet. Oliver gripped his jacket once more and the two of them began to descend as quickly as the slippery steps would allow them. The next few minutes seemed never-ending. They soon lost count of how many steps they had descended but, after a while, they started to get the feeling there were more than they had climbed up. What if they never left the tower, just like the message they had read predicted? Although that didn't seem possible, Rodrigo couldn't help the irrational fear from invading his thoughts. He needed to get out as soon as possible. The stone walls were starting to overwhelm him and the staircase appeared to be getting narrower and narrower. When he started to think about closing his eyes like Oliver, he finally saw the light of the outside world just a few metres below them. He was tempted to run down the remaining steps but he curbed the desire so his friend wouldn't be left alone. Never in his life had he been so eager to see the open sky above his head once more. When they finally exited the tower, they paused and looked at each other with relief. Oliver's forehead was drenched in sweat.

'Phew! I was scared we were never going to get out of there,' Rodrigo confessed.

'What?' Oliver laughed. 'Did you think we were going to find the door sealed with stone and cement?'

'Come on. Don't act so brave. You're still as white as a ghost.'

'I know, but that's down to my claustrophobia.'

'Ok, whatever. Let's get out of here before somebody catches us.'

Rodrigo started to walk but something rolled under his foot, almost making him fall. It was the torch. He bent down to pick it up and found the batteries scattered around them too.

'The cover's missing,' Rodrigo said. He looked around him but he couldn't find it.

'Never mind. Leave it,' Oliver said. 'We should get moving and see if we can get back to our room before the Mole catches us.'

Rodrigo knew it was going to be difficult to achieve. As they hadn't made signals with the torch, Alvaro wouldn't be prepared to throw his second stink bomb. Even still, he wasn't worried. The only thing that mattered was they were finally out of that cursed tower. He felt so relieved that he was ready to face any punishment that came their way. However, luck appeared to be on their side as when they reached the corridor to the bedrooms, they could hear quite a din and the Mole telling someone off. Carefully, they approached the corridor and saw that their way was clear. A moment later, they had made it back to their room unseen. They blindly groped their way towards their beds, removed the backpacks and dived under the blankets.

'You're not going to believe what we saw up there!' Oliver said. 'When we lost the torch, a message written on the wall appeared. It was like it was written in luminous ink. It said–'

'Don't talk rubbish!' Sergio interrupted. 'I've been watching the tower the whole time and I didn't see your light. Obviously you didn't dare go up the tower.'

'Well, you're wrong,' Rodrigo said. 'When I put the torch through one of the holes to signal to you, Oliver pushed me and the torch fell to the ground. But I can assure you that–'

'Yeah, right,' Sergio replied. 'I suppose you at least managed to leave the MP3 player there?'

'We couldn't,' Rodrigo explained, although he was starting to realise how unconvincing their story was. 'We had to use the screen light to go back down the stairs. Look, I have it here.'

'So you have no proof you went up to the top of the tower. Only a story about a mysterious message. I bet you were hiding in the bathroom the whole time, inventing this tale.'

'You can say that to me again tomorrow,' Oliver replied. 'I'm going to convince the guide to let us go up to the top of the tower, then you'll see for yourselves.'

'They won't be able to see anything,' Rodrigo said. 'The message on the wall can only be seen in total darkness. We only saw it when the torch fell.'

'Oh, come on!' Alvaro mocked. 'You've got an excuse for everything.'

'You two can go up there tomorrow night!' Oliver insisted. 'Then you'll see the message with your own eyes. I think it's the key to finding–'

But Oliver couldn't explain his theory to them as just then the Mole knocked on the door and told them to be quiet once and for all.

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