Excitement. Nervousness. Joy. They weren't Dean's emotions, he didn't feel them – but they were there. Someone, somewhere, was jittery with anticipation, and at the same time happier than they'd ever been before.

Why did he know what this other person felt?

Someone pushed him aside, guided him with dispassionate hands on his shoulders to slump against the wall. Ian, Dean remembered, the guy's name was Ian. He was the leader of Dean's Sharing group at school. And he'd been one of the people who had just pushed Dean's head into the basin of revolting grey water still sitting on the table.

What is this? Dean wanted to ask him indignantly. Is this some sort of hazing? Some sort of initiation ritual you make all the new members go through? I thought the Sharing was supposed to be against all that sort of rubbish.

But he couldn't say anything. He moved his mouth, and made nothing but a vague "Uhhh" noise. Then he couldn't move it at all. He couldn't even make himself sit up straight against the wall. He could see, though, and what he saw was one of the other kids from school having his head pushed into the basin as well. He was held under for some moments, his arms wrenching against the two older members holding him. Then he stopped moving, stopped fighting, and the two older members put him aside.

But all of this seemed to be rather distant, and he was distracted by the emotions he could still feel, emanating from something outside himself. Something other.

‹Ah!› he thought he heard. ‹Ah-hh!› Disbelief and joy. Bliss.

Dean's eyes moved, twitching in their sockets under their own volition. They couldn't seem to decide what to look at. They moved jerkily from the bright red shirt one of the Sharing people had on, to the yellow poster on the wall, to the patterns the light from the window made on the ceiling, to some girl's jeans, to a hand as it pushed that girl's head down into the water...

Dean's own fingers twitched. They flexed, closed into a fist, drummed against the floor.

That was the thing that finally scared Dean.

What's happening to me? he thought. I didn't do that! Am I paralysed? Have I got some sort of brain injury? Oh no...

He tried to still his fingers, but there was no response. Nothing! They might as well have been somebody else's hands. They pushed against the floor, and suddenly his arms were in on the mutiny as well, straightening his back against the wall.

After a few seconds, his body tried ineffectively to struggle to its feet.

What the hell! Dean cried. How is this possible? No, stop, how is this happening? Frightened, he tried to freeze, like an animal in the headlights of a car.

His body figured out what it was doing and stood. From that other place came a pulse of satisfaction, pride, and more wonder.

Of course! It was so obvious, how could have not have seen it? They were one and the same.

‹Stop it!› he called to that place, that mind, the source of the pleasure and concentration that was sitting inside his mind like a little walled-off tumour. ‹What are you? Who are you? Please, stop!›

He felt a jolt from that mind. Surprise.

‹Yeah, you!› Dean said. ‹Stop that. What the hell do you think you're doing?›

After a moment when it wavered, the mind swept on. It was making Dean's body lean against the wall with one hand, as if it was still unsteady on his legs.

"How are you doing..." It was Ian. He consulted a clipboard. "... Desca four-three-zero-two?"

"Mmmmnh," Dean heard coming out of his own mouth. He straightened up, squared his feet, and tried to speak again – all despite his own efforts to stop it. "Muh?"

Then there was a new feeling – something disturbing his mind, poring through it, looking for something.

"I – am – fine," his body said. "No... problems to... to report."

"Good," Ian said crisply. "Get a move on, you're supposed to be out of here in a few minutes." He moved on to the next person, a boy Dean knew vaguely from school, who was slumped against the wall staring at his hands as if he'd never seen them before.

‹No problems? No problems?› Dean demanded. ‹What is this? What's going on?›

Help, he tried to call. Help me!

He steeled himself and tried again.

"HEL-mph," he said. The mind clamped tight on his mouth.

‹Let me talk!› Dean said. ‹Get out! Let go, go away, stop it! Who are you?›

There was no response – but the feeling started again. It was like being touched in a place you didn't know you had, Dean thought, dazed. If someone had told him yesterday that you could feel someone touching your memories he would have said they were crazy, but that was what was happening. The other mind was flicking through them as if they were cards or CDs in a shallow box. It didn't hurt exactly, but...

‹Stop it! Get out of there, that's mine!› Mine. Get out.

The mind flinched, stopped for a second, and then kept going. School flashed behind Dean's eyes. Home, his mother, friends... There was nothing it wasn't pushing trough, no memories it couldn't see. It skimmed the surface of most of them, but a few it plunged deep into.

... He was six or seven, at a birthday party. He spilled a drink and watched toxic-looking blue liquid spread across the cheap paper table cloth to a soundtrack of shrill childish laughter.

... He was eleven, and home alone for an afternoon. He put a few millimetres of his mother's port in the bottom of a plastic cup and tipped it onto his tongue, just to see what it tasted like. It was horrible and he spat it out into the sink guiltily.

... He didn't know how old he was. He fell on the rough concrete of the play ground, and scraped bloody lines down his knee. He cried, and burned with shame for it.

... He stepped up onto the stage and accepted the certificate for first place in Biology. The principal squeezed his hand firmly and he mumbled something inane, but the grin on his face was genuine.

‹Get out! Get out, get out! You can't see those!›

... "Bye, Dean, have fun," his mother said. "When will you be back?"

"Ah, probably not too late," he said, checking his pocket for his wallet and glancing at the time. "I'm starting to get... disillusioned with this whole Sharing thing, you know? They're kind of pushy. They keep asking me to get more involved, and they talk like everything they do is bigger and better than anything anyone has ever done in the history of the world." Dean rolled his eyes. "I told Ian that I'd go to this special private meeting about becoming a 'full member' tonight, but I think I'll be backing out."

"Well, why don't you want to become more involved?" she said. "Of course, I can see how it would cut into your extremely busy schedule of..." She paused teasingly. "I forget. What is it you do all afternoon again?"

"Har-dee har, Mum," he grumbled. "I know, I know. I should be back by seven."

His wrist rose and his eyes looked, deliberately, at his watch. 6:45. His eyes rose again to survey the room.

"Hey – Desca," the girl in jeans said to him. "Is that you?"

"Yeah," the invader said with his mouth. "Yes. Yeah. It's me. Tasnik?"

"Yes!" she said. They gazed at each other for a few seconds. The girl had freckles, bleached blonde hair that was growing out dark brown, and blue eyes. Dean didn't know her.

"This is so-!"

"I can't believe we finally-!"

"–amazing-"

"Isn't it incredible?"

They both burst out talking at once. Around them, the other people who'd been dunked in the pool were beginning to do the same. Dean could feel a smile stretching his mouth, could feel the bubbling happiness of the invader.

‹No!› he shouted. ‹No! Hey! Hey, what about me? Don't you ignore me!› What right did that other mind have to feel happy, when Dean was confused and frightened and struggling desperately to move something, anything, for himself?

"I need to go," the invader said, after a few moments. "This host is due back to his home soon."

Ian glanced over at him. "Yes, go. You know your orders for the moment – we'll sort out schedules at the next Sharing meeting. Do not miss it."

"Yes, sir."

The invader piloted Dean's body out of the room – it was a classroom at Dean's school. Dean wished, now, that he'd been a bit more insistent about going home earlier. He wished he hadn't told Ian he'd come to the private meeting. He wished he'd been just a little suspicious when Ian had brought them inside the school when they were supposed to be staying in the barbecue area.

Dean braced himself against his own body. ‹No. No. No,› he said. ‹We're not doing this. We stop, right here. This stops.›

He managed to hold one leg still, tripping himself. His body stumbled and fell forward. Dean went to throw his arms out to catch his weight – but the other mind fought him back, with the end result that Dean landed heavily on his shoulder without even a half-hearted attempt to stop it.

‹Oww!›

Dean heard that other voice, bright with shock.

‹Hey!› he said. ‹I know you can hear me, don't bother pretending you can't!›

‹Quiet,› the other mind said absently. ‹That hurt!›

‹No shit, it hurt,› Dean said. ‹Don't move or I'll do it again! Who are you?›

The invader made Dean's body get up. It was so strange, to see the pale tan arms and legs moving about in front of his eyes: they didn't feel like his anymore. Dean mustered all his strength to try and trip himself again, but it didn't work. The other mind was ready for him now.

‹Please! Listen, come on, just stop doing that and talk to me,› Dean pleaded. Maybe politeness would work better. Weren't supernatural entities supposed to be big on manners? He couldn't believe he was thinking that. Supernatural entities? ‹Please, will you stop controlling my body and answer me?› His ankle throbbed with pain, and his shoulder did as well where he'd struck it on the floor.

There was no answer, and they continued down the hall, out the swinging door and into the darkness outside. Dean would have stopped and waited for his eyes to adjust, but the thing controlling him now had other ideas. It paused to rake through Dean's memories again, and then headed to the barbecue area where he'd left his bike.

Ian had acted so... weirdly tonight, Dean thought. In all their previous interactions Ian had always had this eager, goofy grin on his face. One of those people that just oozed enthusiasm for whatever task they were currently doing, and managed to get that enthusiasm all over everybody else a surprising amount of the time.

It must be an act, Dean realised, as he was carried along into the cool evening air. It was dark already. Ian had been like that as long as Dean had known him. For how long had he been one of Them? Because it was increasingly clear that there was a Them, and that Dean was now one of Them.

‹What are you?› Dean cried. ‹What the hell are you?›

Finally, the mind deigned to answer. ‹I am a yeerk,› it said proudly. ‹I know that you don't know what that is, so I will explain. We are an alien species, much more technologically advanced than you are, and we are taking over your world. You are now my host. As we speak, my body is wrapped around your brain, controlling your every movement, overriding your commands. Your body is mine and I will do with it what I wish, and I would advise you to stop making such a fuss.›

‹What?› Dean said. ‹No... no, I don't believe you! This is too crazy!›

‹Believe what you like,› the alien said as it wheeled the bike onto the road. ‹It's nothing to me.›

OOO

They got home by seven, like Dean had said he would. There were lights on in the kitchen and living room. The imposter climbed up the three short steps to the front door, and went in.

‹Now we'll see!› Dean said desperately. ‹Now I'll get rid of you!›

His mother was in the living room, curled up on the couch with the remote.

"Hi, Mum," his voice said. The alien coughed to cover how rough his voice was – rough, because Dean was bringing all of his will to bear on it. ‹Help! Mum, help, something's happened!›

"Oh, hi, Dean," she said brightly. Just as if nothing was wrong. "How was the barbecue?"

"Uh... good," the alien said.

‹Mum?› Dean cried. ‹Mum! Can't you tell something's not right? Come on! Ask me! Ask me if I'm OK!›

"I'm going to stay up a little longer, watch some TV. You want to watch a movie together or something?" Mum said. "You can pick." She smiled at Dean.

‹Mum!› Dean said, disbelieving. ‹It's not me! Damn you, Mum, can't you even tell when I'm not myself? Literally?›

The other mind, the yeerk, was nervous. It spent a long time going through Dean's memories, memories of how Dean usually spent his nights at home. "Nah," it said eventually. "Think I'll head to my room. Do some homework. Maybe get an early night."

"OK. Good night, sweetie," she said, smiling up at the imposter. "I probably won't see you in the morning because I have early shift."

‹Mum! Mum!› Dean yelled in his head. He tried, he tried so hard to say it aloud. ‹Mum, help! Help me! Help me!›

"Good night," the yeerk said. It smiled at his mother, then turned and made its way towards Dean's bedroom.

‹No! No! No!› Frantically, Dean lunged back for the couch, taking advantage of the yeerk's sudden, fleeting relief at having successfully fooled his mother.

No!› The yeerk scrambled for control, panicked.

"Mum!" Dean managed to whisper through a tight throat. He fell backwards and landed awkwardly in the hall with a THUMP.

"Dean? Was that you?"

‹Yes! Yes, Mum, help!› Dean sobbed.

"Oh... yeah," his voice said instead, breathless. "Just tripped on the rug." It laughed weakly. Dean's heart was pounding, his hands shaking as he rolled over and stood up. The other mind against his was aflutter with panic.

"Oh! Are you all right?" his mother called from the couch.

"Yeah, I'm fine!" the imposter said quickly. "Just fine! No problems. Good night!"

The alien drew his door shut behind them both and stood with its back to it, in the darkness, just breathing for a few minutes.

‹No!› Dean screamed. ‹You can't do this to me! Let me go, get out! Get out of my head!›

The yeerk switched on the light and swept the room with its – with Dean's – eyes. Dean railed against it as it noted the roughly made bed, the bookshelves, the desk covered in papers and pens, the bedside table and the dish on it that contained his keys and small change. The school bag lying like a dead thing in the middle of the floor beside his school shoes.

It went and sat on the bed, pulled his schoolbag towards it. One by one, it pulled out all the books, looked at them, laid them on its lap and turned the pages.

‹Noooo!› Dean said. ‹Why are you doing this? Why? Get out!›

‹That was a pointless endeavour. › For only the second time, the yeerk was addressing him directly. ‹ You will not catch me off guard like that again, human. Even if you could, you cannot maintain it for more than a few seconds.›

‹This body is mine,› Dean snarled. ‹Go find your own!› He couldn't believe it. He had been so sure his mother would recognise that there was something wrong. There was always a tell tale sign of mind control in the movies - a light in the eyes, a robotic quality to the voice. Something, anything. If nothing else, it would slip up eventually. How could his own mother fail to realise that her son wasn't her son anymore?

‹No,› the alien informed him. ‹You don't understand. I have all your memories. I know everything you do. I know what you would do in every situation. I am you, now.›

‹No! No! No!›

The yeerk put him aside and stood. It prowled Dean's room, running fingers over the surfaces and picking things up to look at them. Dean didn't know what it felt. He was too wrapped up in his own feelings. To him, the yeerk seemed as unmoved and unmoveable as a rock, while Dean raged and screamed abuse at it. It laid Dean's body down on the bed and pretended to sleep.