It's been three weeks since we moved into the hospital, and things have started to change. Every weekday the children under fifteen have lessons from the teachers that live there, and anyone fifteen or older has to help out with making food, patrolling the gate accompanied by a police officer, tidying rooms, carrying supplies from floor to floor and playing with the younger children. The older children would've also had lessons, but there weren't enough teachers to teach them.

My favourite job is patrolling around the walls with my some of the guards, especially Tom. He always cheers me up and makes me see the bright side of things. Sometimes he lets me pretend to shoot at a few of the infected people and even though I wasn't actually shooting, he would praise me for holding the gun properly or for having good posture. Today we're slowly walking around the perimeter to check for any incoming infected and non-infected people when of them rushes over to us while I still have the loaded gun in my hand.

"Try to shoot it. It isn't that far away, I know you can."

"I don't know what to do!"

"Just try." I take a deep breath, raise the gun to my eye level and pull the trigger, a loud bang ringing through my ears. The bullet hits the ground on the first two attempts, the next three flying past it. I aim slightly to the left in hope of actually hitting it, the bullet shooting out of the gun with so much force I almost drop it.

The bullet hits its knee, but it continues walking undamaged, only slightly slower than before. I aim higher this time, each bullet hitting slightly higher into its body. Finally, after wasting fifteen bullets, I manage to shoot a bullet through its left eyebrow. I should feel happy that I actually hit it, but instead, I feel bad for wasting so many bullets.

"Well done Lil. You're a natural!" I give him a sarcastic look and give the gun back, worried that I could get distracted and shoot myself.

"Why don't they die when you shoot their hearts?" The question has been on my mind since the beginning, but until now I never had anyone knowledgeable enough to answer it.

"What we've been told is that they don't rely on any of their organs to survive, only the brain."

"How is that possible?"

"I don't think anyone knows the answer to that. We just know that if you shoot them in the head or sever the spinal chord, they die."

"If their hearts can stop beating, then doesn't that mean they're dead?"

"I guess so. But there's probably a more scientific explanation, so don't take my word as gospel."

"When are you going to show us how to use weapons?" Tom looks down at me with a strange expression, a mixture of worry and pride. I feel bad asking so many questions, but I've been meaning to for so long and now I can finally get them off my chest.

"Train? Why would you need to train? That's our job, not yours. You're only fifteen."

"What if we're attacked and I need to help? I can look after myself, Tom. I want to help."

"Lilly, you're safe here. You won't be attacked, you don't need to fight. The adults can handle everything, okay? Do you understand?" I have an urge to punch something.

"Do you think that I can't do it because I'm younger than you? We need to know how to defend ourselves!"

"No, you don't! You're not in any danger here, and you never will be!" I storm off and march to my room, feeling like a spoilt teenager who's not allowed to go to a party. I sit down on the bed and pull the knife from my bag, examining the slightly stained handle. He can't stop me training by myself, so I just have to do that more often.

I walk to the empty storage room, take the knife from my sleeve and stab the pillows that I'd stuffed into the shelves. I carry on for another ten minutes, my attacks gradually becoming weaker, until I'm too tired and collapse onto the floor. It's good for relieving stress, but it tires me out very quickly.

I lie there for a while, thinking about the thing that I'd shot, how it fell to the ground, not moving. I shudder and raise myself to a sitting position, but stop when I hear footsteps behind me, slowly approaching. I raise my knife in front of me, ready to attack as a teenage boy appears from behind another shelf.

"Were you watching me?"

"No! Well... kinda. I came in here to read, but then you walked in and I didn't know what to do. I thought I could sneak out while you were on the floor, I'm sorry. You're pretty good at fighting from what I've seen, do you think you could teach me a few things?" He has brown hair, he's tall and skinny and is wearing a Jurassic Park T-shirt with jeans and red converse.

"Fine. I just finished, but you can meet me here tomorrow at 3 pm. I can try and teach you some things."

"Thanks! I won't be late." He awkwardly walks away, clutching his book to his chest. I don't really want to share my secret room with anyone else, but it's probably a good idea to start making some friends. Maybe I could try and help Ruby as well, but not tomorrow. I tuck my knife into my sleeve, check that it's not visible and walk back to the room. I think again about the infected person that I shot. Infected person? I have to think of a better name to call them than that.

The thing that worries me the most is that the police still haven't found my parents. They told me that all the airports have been closed by now, which means that they're stuck in Hawaii until it's safe to come back. I try and forget about the fact that I might never see my parents again and about the increasing threat only a few metres away from us. Thinking about everything now will only stop me from sleeping, which is all I need right now.

I carry on walking, eager to lie down and take a nap, before having to play with some toddlers in the nursery section. I remember the boy that I met and realise that I forgot to ask his name. Never mind, I can do that tomorrow. People constantly assure me that we're safe from anyone unfortunate enough to be infected, but I can tell that their numbers are increasing. Every day more of them appear along the treeline and at the gate. It's as if more people are infected every day. No matter how many people tell me not to worry, I can't get rid of the gut feeling telling me to stay on guard.