The rain didn't stop overnight, or the next day. Lily and I stayed indoors and played games. At least my little garden was getting some water. I was pleased we had been for a picnic while the weather had allowed us to. The weather forecast had predicted a storm, so we weren't planning to go anywhere any time soon.

"I'm really sorry girls," Mum said as she walked into the snug where we were playing draughts. "I know I said I'd make you a spaghetti bolognaise, but I've run out of tomatoes."

"No problem," I replied, smiling at her. "Lily and I can go to the shop and get some before the storm hits."

"It's raining though," Mum said. "Are you sure you want to?"

"Sure, I'd rather get a bit wet and have the bolognaise," I told her.

Lily and I made sure we had on our jackets and, picking up two umbrellas, ventured out into the rain in the direction of the shop. The dark grey clouds were swirling slowly in the sky, suggesting the weather forecast had been right about the storm.

Fifteen minutes later we had picked up the tomatoes and were starting to make our way back home.

Suddenly I felt a hand clasp over my mouth, and I was yanked backwards, dropping the tomatoes. I made a noise loud enough for Lily to hear, and instinctively kicked backwards to try to hurt whoever had a hold of me.

The man with the dark eyes yelped in pain and let me go. Lily grabbed my hand and we started running through the rain to get away from him. We ducked into the doorway of a large, abandoned warehouse to hide, but he was still coming towards us, so we knew he'd seen our hiding place.

Lily looked around.

"This way," she said, pointing up the stairs behind us.

Together we climbed the wet stairs as the man continued to follow us. At the top of the staircase was a door that led to the rooftop. We tried the handle and it opened easily. We fell through the door and kept running.

The wind was howling, and thunder clapped in the distance. The storm was coming. I looked around for a place to hide. But we'd stopped for too long, and he was nearly behind us.

Lily pushed me behind her back, so that I could use her as a shield.

"Let me past," growled the man. He was clearly more concerned about attacking me than Lily, but I still didn't understand why.

"Don't you understand? Killing her is pointless! There's no way to go back!" shouted Lily against the loud wind.

The man turned his dark eyes to look intently at me. He looked back to Lily, lifting his finger to point at me, as I shivered behind her.

"Did she destroy it?" he asked just as loudly.

Lily looked briefly over her shoulder at me and then back at the man. "Yes," she nodded.

What? They were clearly talking about me, but I hadn't destroyed anything! What was Lily doing? Why was she saying these things? I was so confused, but I just watched them in shock.

The wind blew my hair into my face and more thunder sounded, closer this time. The rain was falling thicker and faster as the storm intensified.

"No!!!," wailed the man, obviously distressed at whatever I'd apparently destroyed. "No! No! No!"

"Yes," replied Lily. "Which means even if you kill her, what happens next? You're still trapped here."

"You stupid girl!" shouted the man. "That means you're trapped here too!"

"I know," responded Lily. "But I knew that when I followed you here. You know I can't let her die. It was a price I was willing to pay to keep her safe." She was pointing at me.

"So, neither of us can go back," said the man, angrily. "But I'm curious to know - what happens to you if she dies now?" He tilted his head to one side thoughtfully and looked straight at me while still talking to Lily. "We both know you can't exist without her."

Now I was really confused. I had always felt like there was a connection between me and Lily, but he made it sound like if I died, so would she? And this man seemed to know it. I didn't understand how it was possible, but the way he was looking at me, I knew it was true.

I backed up towards the edge of the roof as he started coming towards me. A bolt of lightning lit up the sky for a second, and thunder followed quickly afterwards. The rain pummelled us all relentlessly, and it was so thick I could barely see through it anymore.

"Stop!" shouted Lily, but he ignored her and started coming at me faster.

I froze on the spot. I knew I should probably run, but there was nowhere to run to. I was too close to the edge.

A second later I was on the floor with Lily on top of me, shielding me. She must have slowed time down and pushed me to the ground. The man slipped on the wet floor at the place I had been standing and fell over the edge of the roof. I heard a thud through the rain as he hit the floor below.

"Are you OK?" asked Lily, getting up. She reached out a hand towards me to help me onto my feet.

"Yeah," I replied, shivering in my wet clothes.

We looked tentatively together over the point where he fell. He was motionless on the ground beneath us.

"Is he ....?" I couldn't say the final word.

"I didn't mean for him to die," said Lily, sadly. She turned to me. "But it means you're safe, so my mission is finished."

I wrapped my arms around myself as I watched the rain continue to fall around us. "Your mission?"

Lily put one hand on each of my shoulders. "My mission was to protect you from him. He won't be trying to hurt you anymore. Which means it's time for me to leave."

"What?" I couldn't believe what I was hearing. "I thought we had something special! A connection? You said you felt it too? Doesn't that make you want to stay?"

"Of course it means I want to stay," she hugged me gently and then moved away again. "I want to stay with you forever, but it can't happen. What I want to happen and what needs to happen are two different things."

My brain started sorting through all the things that had happened as we stared at each other in the rain.

"Both of you ...you and him, turned up in my life on the same night. That wasn't a coincidence, was it?" I asked, although I felt like I already knew the answer.

"No," she replied. "I followed him. I knew he'd be trying to get to you, and I thought it was better if I found you first. I was thrilled when I found you in the library. I followed you home that night to make sure I could keep you safe if he tried anything. I'm so glad I did."

My head spun.

"You were looking for me? You knew about the connection before we met in the library, didn't you?"

"Yes," she admitted.

"You knew I didn't like cola before you even met me, didn't you?" I realised.

"I knew a lot of other things too," she acknowledged, nodding.

"Why was he trying to kill me? That man – you know who he is, don't you?"

"Yes. But I can't tell you Caroline. Not yet, anyway. I'm so sorry. It's ... complicated."

I felt like I didn't understand anything. So many questions and no answers. I started to cry.

"The last thing I wanted to do was upset you," said Lily. "But I do need to go now. Please understand that if everything works out the way I expect it to, we will see each other again. One day you'll understand. I intend to explain it all to you when we meet again."

Lily unclasped the necklace from around her neck.

"You must never tell anyone about me. No matter how tempted you are. Nobody can know I exist yet, Caroline. This was never supposed to happen. Please tell me you understand."

I nodded while she clasped the necklace together so that it was now hanging around my neck.

"I want you to have my necklace," she said.

"But it's the only thing you have of your mother's," I said, knowing how much it meant to her.

"And now it's yours. I want it to remind you how much you mean to me. Please look after it. Maybe one day you'll care about someone enough to pass it on to them. Until then, it's yours."

She flung her arms around my neck one last time, and I relished the hug. The tears I cried were being washed away by the rain. The sobs were coming thick and fast. I could hardly breathe, let alone talk.

And then she was gone, and I was alone.