Rodrigo felt as though someone was gripping his arm and he tried to shake them off with all his strength. He had to escape from this cursed place.

'Wake up, Rodri! It's nine o'clock already.'

As soon as he opened his eyes, he was confronted with Oliver's face half a metre away from his own. He looked around him, not completely understanding where he was until he finally made out the room he had been sharing with his three friends. He was drenched in sweat, obviously due to the nightmare that had tormented him during the night. It had been as clear as real life. He had been descending the stairs in the tower, but no matter how many steps he went down, he never found the exit. Meanwhile, a few words had continued to appear before his eyes every few metres. The stars will fall from the sky before you can leave. The moon will rise in the day before you can flee.

'Are you alright?' Oliver asked.

'Yes, it was just a nightmare. I'm fine.'

During breakfast, their classmates who had been sharing the bedroom next to them were still discussing who had thrown the stink bombs. Rodrigo and Oliver couldn't help but laugh.

'What are you two laughing at?' one of them asked.

Rodrigo could feel his cheeks starting to fill with colour. Fortunately, Oliver knew how to react.

'Are you sure they were stink bombs? Maybe one of you can't control their bowels?'

'Very funny. Was it you? You were all in the room next door. I wouldn't bet against you having found a hole in the wall.'

'You know what they say, right, Andres?' Oliver replied. 'Whoever smelt it dealt it.'

Luckily his comment had the desired effect and the others in the group returned to blaming each other.

'Very good, Oliver,' Rodrigo said quietly.

'We'll need a different plan tonight,' he commented. 'If we throw stink bombs again, they'll suspect us and they'll tell the Mole.'

'You mean you want to return to the tower?'

'They have to see it,' Oliver replied, motioning to Alvaro and Sergio. 'Maybe with all of us there, we'll find the secret passageway. I think the key is in the stars. If we could get our hands on a map of them that shows the constellations–'

'What are you saying about stars?' Alvaro laughed. 'I'm starting to believe you did go up the tower, but you must have fallen and hit your head on the stairs.'

'Right,' Oliver said. 'You don't understand because we didn't have time last night to tell you what the message said. It was something like, "Follow the path of the stars when you hope to leave, and... and..." Well, then it said something about the moon. I don't remember it exactly.'

Rodrigo started to laugh. Oliver was as bad at remembering mysterious riddles as he was at memorising river tributaries.

'"The stars will fall from the sky before you can leave. The moon will rise in the day before you can flee",' he recited. 'That's what was written on the wall.'

'That's it,' Oliver confirmed. 'What a great memory you have, Rodri!'

'That doesn't seem like a clue to finding the secret exit to me,' Alvaro stated. 'Surely the count wrote the message to torment the prisoners.'

'Do you mean you believe all their tales now?' Sergio asked him. 'I'm telling you the two of them didn't get any further than the bathrooms.

'What do you bet?' Oliver challenged him. 'What do you bet that we'll return tonight with a camera phone and show you it's true?'

'We're going to return?' Rodrigo repeated. He could already sense Oliver's intentions. 'What do you mean "we"?'

'The two of us, of course.'

'Why are we talking about this again? There's no way I'm going back up that tower! Going up it once is more than enough for me.'

'Shh,' Oliver interrupted. 'Be quiet! Here comes the Mole!'

After that, they didn't have another opportunity to talk about it further, which was a relief to Rodrigo. After breakfast they had a juggling class and then a pottery workshop. It was turning out to be a much more entertaining morning than the previous day, when the only thing they had done was listen to the guide's explanations about the castle. But nothing could help Rodrigo concentrate. His thoughts continued revolving around the previous evening's adventure and it seemed as though the same was happening to Oliver. The urn Rodrigo made in the pottery workshop was in the shape of a toilet, while Oliver's pitcher looked like a pig's head. When Andrea, one of the girls in the class, came over to them, Rodrigo tried to hide his urn so she wouldn't see it. Fortunately, she only noticed his friend's pitcher.

'Hello, Oliver,' she said, gently pushing her long, brown hair out of her face. 'That's such a cute, little pig! Is it a piggybank?'

Oliver looked at her, entranced, before muttering a response that nobody managed to catch. Rodrigo, Alvaro and Sergio burst into laughter.

'What's up with you lot?' Oliver asked them, his face as red as a tomato.

Sergio was about to respond with a witty reply but just then the Mole entered the room and stood in front of them, waiting for their attention like he usually did when he was about to announce something important.

'I have good news,' the teacher said. 'Tonight, we will be going to bed a little later than usual. It's going to be a perfect night for observing the Geminids and we are in the ideal place to see them.'

The whispers that followed clearly indicated that Rodrigo was not the only person in the room who had no idea what the Geminids were. Obviously, the Mole knew this because he openly smiled when he saw the perplexed faces of his students. Without a doubt, something strange was happening to their history teacher. A few months ago, seeing him smile would have been regarded as a miracle and he had never thought about letting them stay up late. Not for all the Geminids in the world.

'Does anyone know what the Geminids are?' the teacher asked, but after a few seconds of silence he had to provide an explanation. 'The Geminids are a meteor shower that takes place every year on the 13th or 14th of December.'

'What's a meteor shower?' Oliver asked, without raising his hand, as he always failed to do.

'Meteor showers are points in the year when we can observe a great number of meteorites. When you see a meteor shower, it seems as though the stars are falling from the sky.'

Rodrigo felt as though his body had frozen from head to toe. The words written on the wall of the tower came rushing back to him when the teacher stated those final words.

The stars will fall from the sky before you can leave...

Rodrigo glanced at Oliver, believing he would have made the connection too, but his friend seemed to be carefully observing the cobwebs on the roof. He probably hadn't been listening to a single word, despite the fact it was him who had asked the question.

'The Geminids are not as famous as the Perseids, which are also known as the Tears of Saint Lawrence,' the Mole continued. 'This is not because they are less important, it is due to the fact they normally cannot be seen as easily because there is usually a lot of cloud cover in December. Today, however, we have a completely clear day and one other thing in our favour: tonight, there will be no moon.'

'How is that possible?' asked Oliver, who appeared to be paying more attention than Rodrigo had previously thought.

'If you had been paying more attention in science class, you would know that every twenty-nine days there is a moonless night,' the teacher replied. 'It's called a new moon.'

'So shouldn't it be called a disappeared moon?' Oliver asked, making many of them laugh.

'Well, in reality the moon doesn't disappear. It merely appears during the day instead of at night. In fact, the moon is in the sky right now but the glare of the sun doesn't enable us to see it. For the same reason, we cannot see the stars during the day, although they continue to be in the sky.'

Rodrigo froze. That was exactly what the second part of the message had said: The moon will rise in the day before you can flee. First the stars and now the moon... It couldn't be a coincidence! Without thinking twice, he leaned towards Oliver and asked him quietly,

'Did you hear that?'

'I told you so!' Oliver replied. 'This guy is nuts. Everyone knows the moon only comes out at night.'

'What? Haven't you realised what he said?' Rodrigo insisted. 'It's what the message inside the tower said! The moon will rise in the day before you can flee.'

'You're right!' Oliver exclaimed. In his surprise he had forgotten to keep his voice down. 'The stars will fall from the sky and the moon will rise in the day. It can't be a coincidence! Something's going to happen tonight!'

'I'm glad you're so passionate about astronomy, Oliver,' said the Mole, 'but if you continue to interrupt me without raising your hand, you won't be allowed to watch the meteor shower. Now, let's eat.'

'I still can't believe it!' Sergio said as soon as they reached the dining room and sat down. 'I'm sure you both knew he was going to talk about a meteor shower and a new moon today. I bet you heard the Mole talking to someone and you thought you could wind us up with a joke.'

'I don't know,' Alvaro hesitated. 'If they're lying about this then they're fantastic actors. Didn't you see the look of surprise on Rodrigo's face when the Mole said that thing about the stars?'

'Of course,' Rodrigo said. 'If you were in my shoes you'd have done the same. You know what. Now I think Oliver's right. I think the tower has a secret passageway, but for some reason it can only be seen tonight so I'm going to be there to find it. Who's coming with me?'

The excitement of their discovery had made Rodrigo forget fully about the fear he had experienced the night before. He was sure that tonight, after the meteor shower, something would enable them to find the tower's secret passageway and there was no way he was going to miss out on the opportunity.

'I'll be there, of course,' Oliver said.

'I think I'll go too,' Alvaro nodded. He seemed to be becoming more and more convinced that it wasn't a joke.

'Ok, I'll go too then,' Sergio finally conceded. 'But let's be clear that I still don't believe your stories but there's no way I'm going to be the only one staying in our room.'

Rodrigo placed a hand over his mouth to hide his smile. It was obvious Sergio was beginning to doubt his own words but he wasn't willing to admit it.

'How are the four of us going to be able to leave our room without someone catching us?' asked Oliver. 'We can't use stink bombs again. They're too suspicious.'

'We could escape while the Mole is taking us to see the meteor shower?' Alvaro suggested. 'We could say we left something in our room, or that we have to go to the bathroom.'

'I don't think that will work,' said Oliver. 'If I'm a part of the group, the Mole won't trust any excuse we invent. He always thinks I'm up to something.'

'I wonder why?' joked Rodrigo.

'I don't know. He must have confused me with someone else,' Oliver replied, forcing a naive expression.

'Well, we have to think of something,' Rodrigo insisted, putting an end to the jesting. 'Today we could possibly solve a mystery that has been hidden for hundreds of years.'

'The guide told us that the investigators have searched the tower many times,' said Sergio. 'If there really was a riddle written on the wall, they would have found it.'

'Maybe they never thought about searching at night,' Oliver said.

'That's true,' said Rodrigo. 'If they've inspected the tower I don't think they would have done it in the dark. Even if somebody had gone up to the top of the tower at night they must have taken a torch.'

'So how are we going to do it?' Sergio insisted. 'If the four of us want to go, there won't be anyone left to distract the Mole.'

'There are always the ghosts,' joked Oliver. 'Since you get on so well with them, you could ask them to make a bit of noise to distract him. You know, howling, moaning, banging on windows...'

'Of course!' Rodrigo jumped, having just thought of a plan. 'That's it! We can record electronic voice phenomena!'

Oliver looked at him with a mixture of surprise and exasperation.

'I was joking, Rodri. Don't tell me you believe in this nonsense too?'

'No. Listen. We can take the MP3 player and record voices that sound like ghosts. Then we can leave it hidden in the girls' bedroom and when they start screaming with fright, the Mole will have to go and see what's happening.'

'Ok, but we're still in the same position,' Alvaro objected. 'How are we going to hide the MP3 player without anyone noticing?'

'We'll do it just after dinner,' said Rodrigo. 'We'll try to finish quickly and go upstairs before everyone else.'

'But it's no use at dinner time,' Alvaro argued. 'It has to be at night when everyone is in bed.'

'Oliver. You said your MP3 player can record for a long time continuously, right?' asked Rodrigo.

'Up to ten hours.'

'So first we need to leave two hours of complete silence before recording the ghost sounds. Then we'll be able to hide the MP3 player at dinner but it won't make a noise until twelve o'clock.'

'What a great idea, Rodri!' Oliver said. 'I think the next time I want to escape from the boarding school, I'll consult you first.'

'We still have one problem,' Sergio objected. 'The bedrooms are locked with a key. We won't be able to enter them to hide the MP3 player.'

'Maybe Oliver could get Andrea to invite him in...' Rodrigo laughed.

'Ha ha, very funny,' he replied, turning a beetroot red.

'We need to put it inside one of the girls' coats without her noticing,' concluded Rodrigo. 'We can do it when we go outside to see the meteor shower.'

Once they'd all agreed to the plan, they ran upstairs to their room. Oliver switched on his MP3 player, pushed record and placed it inside a drawer.

'After lunch we have some free time,' Rodrigo said when the four of them went out into the corridor. 'We'll return to our room then and record the ghost noises.'

During lunch, the four of them were so excited, talking about their plans, that none of them realised their plates where still full when the main course was about to be served.

'What's wrong with you lot?' asked the monitor. 'Don't you like the soup? You have to eat it all.'

The boys began to eat without complaining but within two minutes they had forgotten about their plates and spoons once more.

'We have to find another torch,' Rodrigo said. 'We found Oliver's torch when we came out of the tower but we couldn't find the battery cover.'

'Don't worry about that,' said Sergio. 'I'll ask my cousin for his. He brought one too.'

When everyone else had finished eating and had begun to leave the room, Rodrigo and his friends had to hurry and finish everything they had on their plates. Within five minutes, they were in their room once again. Oliver opened the drawer without making any noise and pressed pause.

'Ok, it's been two hours already. Now it's ghooooost time,' he said in a deep, ringing voice, drawing laughter from his friends.

'Alright,' said Rodrigo after a few seconds. 'As soon as you press record, we'll take turns to moan, scream, cry, beg for help and everything else lost souls say or do.'

Oliver pressed play on the MP3 player and Alvaro started to wail like a ghoul, then Oliver shrieked like a child, saying, 'Help me mum, please,' and none of them could help but laugh. They had to rewind and start again. This time, they lasted ten seconds before Oliver said, 'I'm thirsty for blood,' when they all burst into laughter again.

Following many attempts, they finally managed to record two consecutive minutes of voices, wails and moans. Oliver rewound the recording to listen to the result and they all looked at each other, satisfied.

'We've not finished yet,' Rodrigo said. 'This will distract the Mole and make him leave the room, but then we have to get back in. We need to record another half an hour of silence then more sounds.'

Following his instructions, Oliver left the MP3 player recording inside the drawer again and the four of them left the room in order to avoid making any sound. Half an hour later, they returned and finished the job, but not without having to repeat it several times.

That afternoon, Rodrigo didn't take in a single word of what was being described to them about the way of life during the Middle Ages. He couldn't stop thinking about the riddle in the tower and he kept asking himself if those same words had enabled Count Zacara and the other prisoner to escape without leaving a trace. The most logical way out would be a tunnel, but something like that couldn't have remained hidden for centuries.

Finally the Mole appeared at the end of dinner and order them to put on their jackets and head out to the castle courtyard. Rodrigo and his three friends were already nervous, asking each other if they would manage to drop the MP3 player into one of the girls' coats without her noticing. When they went outside, they could see that it was indeed a moonless night but the sky was splattered with stars. Fortunately, the thick darkness that surrounded them would also help them to carry out their scheme.

'Come on, Oliver,' whispered Sergio while they were all gazing intently at the sky. 'Now's a good time.'

'Why don't you do it?' Oliver replied, offering him the MP3 player.

'We'll toss a coin,' Rodrigo suggested, trying to avoid a useless debate. 'We'll each toss two coins. The first to get two heads has to do it.'

Oliver argued that he'd done enough already by offering his MP3 player as he still didn't know how he was going to get it back, but as time was of the essence he gave in and Rodrigo was the first to toss the coins. When he got heads then tails, he passed them to Sergio who also got heads followed by tails. Next, Alvaro threw both coins into the air before they showed tails twice. Finally, Oliver tossed the coins... and got heads both times.

'See?' Rodrigo joked. 'Even the coins know you're the most experienced person when it comes to things like this.'

Reluctantly, Oliver squeezed the MP3 player in his fist and walked over to Lorena, the closest girl to him. He stealthily crept up to her back and just as he was extending an arm to reach her pocket, one of her friends turned round and saw him.

'Hey,' she said to him. 'What are you doing?'

'I... nothing, really,' replied Oliver, stepping back a few paces.

'Leave us alone or I'll tell Mr Ramiro,' she threatened.

For a moment, Rodrigo was confused until he remembered that "Mr Ramiro" was the Mole's real name. It had been a while since he'd heard the name used.

'They caught me,' Oliver said as he re-joined them. 'She threatened to tell the Mole so I think the rest of them will be on alert now.'

They couldn't give up. They had to reach the top of the tower that night at all costs. Rodrigo was attempting to think of another way to place the MP3 player in the pocket of one of the girls when an idea struck him. He asked Oliver for the MP3 player and then strode straight over to Lorena.

'Now you?' she protested. 'Won't you leave us alone?'

'I just wanted to warn you,' Rodrigo said, 'Oliver put a beetle in your pocket.'

As he had imagined, the girl began to scream. Quickly, she took off her coat as if it were full of snakes and threw it as far away as possible. Rodrigo walked over to the coat, dropped the MP3 player inside the pocket, then pretended to take the "beetle" out and squash it with his foot.

'There you go,' he said to Lorena, returning her coat. 'But if I were you, I wouldn't put your hand in the pocket again. Beetles leave a horrible smell.'

The girl took the coat, eyeing it with disgust. Instead of putting it on again, she draped it over her outstretched arm as if it were a dirty cloth. Rodrigo returned to his group of friends, smiling.

'Impressive,' Oliver said to him, studying him with the admiration he would normally reserve for the striker of his favourite football team. 'It's a shame you don't use this talent of yours more often. If I had your intelligence, I would turn the boarding school upside down and nobody would suspect me.'

'Well, your fame as a prankster also helped,' Rodrigo replied. 'Lorena immediately believed you'd put a beetle in her pocket.'

'Of course she did,' he said between laughter. 'I did it once to Sara, but with a lizard.'

Thirty minutes later, the Mole declared their evening of star gazing complete. On their way to their bedrooms, everyone was talking about the shooting stars they had seen except for Rodrigo and his three friends who had scarcely had time to look at the sky. As it was already half past eleven, the Mole ordered them all to brush their teeth and be in bed within five minutes. They made sure to obey him without kicking up a fuss to guarantee their plan would work. A short while later, when nobody could be heard in the corridor, the Mole appeared at their door to check they were all in bed. Silently, he closed the door.

'We should stay in bed until we hear the girls screaming,' whispered Oliver.

The four of them remained silent, listening carefully to any sound that reached their ears. From time to time, they heard a small voice or a snigger from one of the other bedrooms, but nothing sufficiently outrageous to make the Mole reappear. It was quarter past twelve when Rodrigo began to wonder if something had gone wrong with the plan. Lorena had probably found the MP3 player in her coat pocket. If that was the case, there was nothing they could do.

'AAAAARRGGHHH!

The hair-raising scream of panic that pierced the castle walls left no room for doubt. The girls were hearing the ghostly voices recorded on the MP3 player. The four boys left their backpacks under the blankets to create a lump shaped like a body in each of their beds then they gathered at the door. Oliver appeared and whispered to them,

'Come on. The coast is clear.'

Once they had walked the corridor without being seen, the rest of the way to the tower was as simple as the previous day. The icy wind whipped their faces on their way to the great stone tower's entrance. Sergio pulled out his cousin's torch and pointed it towards the stairs.

'So? Are we going up?'

Rodrigo hesitated. What would happen if they went up to the top and the secret passageway appeared at the bottom? It seemed the most logical option. It would be strange if the mystery revealed itself in the same place as where the riddle was written.

'Maybe we should split up,' he suggested. 'Oliver and I can wait here while you two go up to the top. We don't know where the secret passageway could appear.'

'Just as I thought!' Sergio stood in front of him with a twisted grin. 'It's all a lie. You never went up the tower at all. You want us to go up to the top for a joke. You're probably planning on leaving us here on our own.'

Rodrigo felt the urge to take the torch from Sergio and hit him over the head with it. They didn't have time to start their argument again.

'Fine, we'll go up! You two wait here and be alert. The secret passageway will probably appear here at the bottom.'

He was enraged because something told him that it would be his friends who would discover the answer to the mystery, but it was best to split into two groups. Before another discussion could commence, he started to climb the stairs.

'Hey, wait for me!' Oliver said.

Rodrigo turned round and saw that his friend was a few steps further down with his eyes shut.

'Oh, I'd forgotten about your claustrophobia,' he said. 'If you like, you can stay here and Alvaro can come up with me.

'No, no. I'll go with you,' Oliver insisted and he grabbed the back of Rodrigo's jacket so he wouldn't have to open his eyes.

Once again, the two friends climbed the steep staircase before reaching the small, circular room at the top of the tower. As soon as they reached the last step, Rodrigo switched off the torch and turned his attention to the wall where he had seen the riddle written the previous night. The same words that had drawn them on this adventure were still there, emitting a faint blue light. Rodrigo looked around at the rest of the room but he didn't find anything else of note.

There's nothing else up here, he thought. If there really is a secret passageway, Sergio and Alvaro will find it.

He couldn't help but feel a stab of resentment towards his friends. At the end of the day, it had been him and Oliver who had climbed to the top of the tower and discovered the riddle. Sergio and Alvaro had done nothing to solve the mystery except for laugh at them and make jokes about their story. It should have been them who had climbed to the top while he and Oliver waited below. But it was too late. It was obvious that there wasn't a secret exit up at the top of the tower, unless you knew how to fly.

After checking there was nothing else that shone in the dark in the room, Rodrigo switched the torch on again and looked at Oliver who had even dared to open his eyes. Suddenly, something strange happened. Rodrigo hadn't even noticed until he saw the terror reflected in the eyes of his friend. It was as though the floor had disappeared from beneath their feet and they were both falling inside the tower. The spiral staircase twisted around them but they couldn't reach out and touch it despite the two of them continuously waving their arms and legs, desperately searching for something to cling onto.

This is it. This is the end, thought Rodrigo, conscious that in two or three seconds they would hit the ground. He knew that nobody could survive a similar fall so he simply closed his eyes, hoping that it would be quick so he wouldn't feel any pain.

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