In the isolation room, a sharp pain scraped through the inside of Elizabeth's skull. She pressed the heels of her hands to both her temples, but it brought no relief. The sensation lasted only a minute, then was gone, but the experience left her unnerved.

In that moment of agony she had seen John entering a transporter, only to be smashed to the ground by what looked like a Bantos rod. For a moment, she'd felt as if she were seeing through someone else's eyes, as if she were actually in the transporter with him, wielding that weapon and striking him down.

Why would she imagine something so horrible? John had been nothing but kind to her; how could she even think of harming him?

Something felt strange inside her. Her brain tingled as if tiny electrical pulses were randomly firing through it. Random thoughts flashed through her mind, thoughts of violence against the Wraith, the Ancients, and the inhabitants of Atlantis. She imagined tearing the room apart, destroying the equipment monitoring her vitals, ripping out the cameras, ridding herself of these inferior beings and becoming something much more than they could ever hope to be.

Recognising these weren't her own thoughts, she tried to signal to the cameras that something was wrong, but found her body unwilling to comply. She sat still and calm, giving no outward sign of her inner turmoil. Memories returned to her now, recollections of her imprisonment hidden from her until this point. She saw images of Oberoth standing over her, his hand penetrating her forehead, and reams of data flooding her mind, instructions and coding rushing into her mind only to be locked away and forgotten. Until now. The Asurans had tampered with her nanites while they held her prisoner, she could remember it all now with startling clarity, the memories and information unlocking as if to taunt her.

She heard thoughts inside her head, Oberoth's thoughts, telling her the people of Atlantis would pay for their audacity and for the cruelty of their predecessors. Desperately trying to block him, she sensed the battle was already lost. She could feel his thoughts as clearly as if they were her own. Though she fought him mentally, she could feel his control over her body already asserting itself. He had crept in there unseen, and now there would be no stopping him. It was only a matter of time before he took full control of her mind and used her to destroy everything she loved.

He laughed, the sound gouging into her brain and mocking her attempts to defy him. His voice told her it was already too late, that they had infiltrated the city, so what little control she could assert would do no one any good.

Atlantis was doomed to fall.

oooOOOooo

'Has he woken up yet?'

'Not yet, Rodney. But he is showing signs that he's beginning to surface. He hit his head pretty hard, so he'll come round when he's good and ready.'

Sheppard heard the voices and slowly pieced the nonsensical sounds together into sentences he could understand. McKay and Keller? Where the hell was he?

One thing he did know for certain was he had a killer of a headache, and felt even more like vomiting now than he had earlier. He lifted his hand to touch a tender spot on the left side of his head, feeling the tug of a blood oxygen monitor on his index finger. Great, so he was in the infirmary. His favourite place to be.

He cracked his eyes a fraction, but the pain caused when light hit them forced them closed again. He decided to just lie there and get his bearings before announcing he was awake, but unfortunately his movements had been spotted.

'He is rousing,' he heard Teyla say.

The sound of her voice brought his memory rushing back to him. The transporter...Bantos rods. She'd hit him! What the hell was that all about?

He snapped his eyes open despite the discomfort the sudden intrusion of light caused, leaning away from her as he spotted her already at his bedside. 'Why'd you hit me?' he demanded, glaring at her.

Teyla's brow crumpled in confusion. 'What do you mean?'

'What do I mean? I mean, why d'you hit me?' he fired back at her, repeating his question.

All eyes turned to Teyla, awaiting her reaction.

She shook her head, looking puzzled. 'You are mistaken, John. I did not strike you; you either lost your balance or passed out in the transporter and struck your head as you fell.'

He stared at her, looking for signs of deception in her expression, but found none. Yet he knew what had happened. Was she really that angry with him after their argument? That wasn't like Teyla; she was the only person he knew who could remain calm no matter what the situation they faced. Perhaps he was wrong. Perhaps he was completely losing it.

'Is it possible he is delirious due to the lack of sleep he has suffered recently?' Teyla asked, he face depicting her usual level of concern.

'Possible? I'd say that's a certainty. I can barely remember my name most of the time,' Rodney blustered. 'Is it possible whatever cause this is...you know...catching?'

'No, Rodney. There's a serious pain in my ass, but it's not contagious...and I'm not delirious,' Sheppard growled, clutching his forehead as an ache pulsed through it. Speaking was painful, the noise of his own voice inside his head triggering wave after wave of nauseous throbbing that left him dizzy and mildly disorientated.

'Not now,' Ronon rumbled, 'But you only just woke up.'

'Not that we can really class that as a rest,' Keller pointed out. 'He was unconscious, not sleeping. It doesn't have quite the same restorative effect.'

'Whatever,' Ronon grunted, 'But now he's awake he should know better than to think Teyla could hit him. He trusts Elizabeth more than he does us these days.'

Hearing his friend make that accusation hurt, but Sheppard had to admit, that was pretty much true where Teyla was concerned right now.

'Well, concussions do leave the sufferer somewhat confused...but I'm sure Colonel Sheppard will realise his mistake once he's feeling better,' Dr Keller interjected. She turned to Sheppard and offered up a sympathetic smile. 'I'll get you something for that head. You have to stay lying down until that concussion's passed, so no running around trying to keep tabs on everything today, okay? Major Lorne has taken over, and he's happy to look after things until you feel ready to step back into the role.'

The way his head felt, Sheppard suspected that wouldn't be any time soon. He closed his eyes and rode another wave of sickness, the light touch of a hand on his arm disturbing him. He opened them again to find Teyla's tiny hand resting on his biceps. 'Are you all right, John?'

A flash of recall – the viciousness in her eyes as he'd heard the whistle of the Bantos rod approaching, too late to duck its blow – made him snatch his arm away from her. He didn't care who thought he was going crazy; he knew different. She'd hit him. But now, rather than anger, he felt a sadness welling in him. Had he really offended her so badly she felt justified in lashing out at him? Wait a minute...this was Teyla he was thinking about. Teyla did not react that way no matter how bad the disagreement...or did she? There had been that one time with Sergeant Bates. She'd punched him, and if he hadn't been there to stop her she might have done much more to the man. But the slur Bates had thrown at her was far worse than anything they'd fought about. He closed his eyes again. If his brain didn't ache so much he might have a hope of working it all out. He supposed he did have to consider the fact he might have been falling unconscious before he saw her swing for him, and his exhausted brain had somehow twisted the real details.

'Well, now you're awake and no longer scaring us witless, I should really get back to work,' Rodney announced, never one to linger long when others were feeling ill. 'I have some nanites to annihilate.'

For a second, Sheppard thought he saw a flash of anger in Teyla's eyes, reminding him of the same look he'd seen cross Elizabeth's face in his dream. It was gone before he could be sure, but he didn't like the fact the flicker of reaction had coincided with Rodney's mention of ridding them of the nanites.

'Yeah, actually, I think I'd like to be alone now anyway,' he croaked, sliding down in his bed. 'I figure I should make the most of this enforced rest time.'

'Well, enjoy your sleep...and don't worry about me slaving away down in the labs, struggling to keep my eyes open.'

Though he meant it as a joke, Sheppard suspected there was more than an ounce of truth in Rodney's words. 'I appreciate everything you're doing, Rodney,' he called after him as the scientist beat a retreat.

'Again with the creepiness!' he heard him call back, bringing a smile to his face.

'We'll go and let you settle down, buddy,' Ronon said gruffly, giving him a friendly punch to the shoulder. 'Stay here and get some rest until the doctor's say you're fit. Hopefully, you'll remember who your real friends are by then.'

Even for Ronon, that comment struck Sheppard as particularly harsh. The big man did have a tendency to speak his mind, but suggesting Elizabeth was no longer someone he should consider a friend was pretty callous. The Satedan began to walk away, but Teyla hesitated a moment or two longer at Sheppard's bedside, a weird smile twitching at the corners of her mouth. 'Take care, John,' she said, the pitch of her voice much lower than normal, and with an uncharacteristic hint of menace.

He swallowed and nodded, watching her go. Was he being paranoid or had those words been as threatening as they felt?

Five hours later, and with his head still pounding, Sheppard was practically climbing the infirmary walls. Waiting until Keller was occupied elsewhere, he took it upon himself to get dressed and discharge himself, despite the protests of the medical staff still present.

He swayed his way out of the infirmary on unsteady legs, barely able to feel the floor beneath his feet. He knew that wasn't good, but with no need to take charge of the city now Lorne had assumed control, he could stumble around to his heart's content without fear of doing any harm. He'd spent the time in the infirmary thinking things through, and he was certain now that he knew what had happened in the transporter, and he knew what he'd seen in the infirmary. He needed to get to the lab and make sure everything was going according to plan.

He wandered to the transporter and, after checking over his shoulder to make sure he wasn't about to be ambushed, he activated it and asked it to take him to the labs.

When he arrived at Rodney's workbench, dizzy and breathless from the effort, the scientist didn't even attempt to hide his surprise or his dismay. 'Sheppard! I can't believe they let you out of the infirmary already – you look worse than ever.'

'Thanks for that, Rodney,' the colonel quipped, leaning heavily on McKay's desk. 'And for your information they didn't let me out; I discharged myself.'

'Well, that was stupid.'

'I can't just sit in bed at a time like this, Rodney. The place is going to hell and I need to do something!'

McKay looked blankly back at him. 'What d'you mean, going to hell? The chair's fixed, the shields are fully operational, Zelenka has fitted the newly constructed components into the hyperdrive to bring it on-line, and...oh...oh, this is about that business with Teyla, right?'

Sheppard could see from the man's expression he was uncomfortable even broaching the subject, but he needed to warn him. 'Something's not right here, Rodney. I know what happened in that transporter. I know she hit me just as sure as I know I'm talking to you now.'

'But why would she do that? It doesn't make sense!'

'I know, I know. You're right. It doesn't make sense. All I know is she's acting weird and I want you to watch your step around her. You didn't see the look in her eyes when you said you were going to annihilate the nanites in Elizabeth. I've never seen her look so mean...except for in the transporter.'

McKay's jaw fell slack, his eyes darting as they did when he began to panic. The only thing Sheppard wasn't sure of was whether he was panicking at the thought of Teyla going 'dark-side' or the fact the colonel was telling him that was what he thought.

'So...so you're saying Teyla might come after me next?' he squeaked, his voice cracking.

'I don't know, McKay,' Sheppard sighed, rubbing his aching forehead. 'I'm not exactly thinking straight right now, but getting Atlantis fully functioning is pretty much in your hands. So, if they want to sabotage things, you're the one to take down.'

'They who?'

Sheppard realised then how little sense he was making. There was no evidence the Asurans had infiltrated the city in any way, yet that was what he felt. Then, a horrible thought occurred to him. He was pretty sure the Asurans could change their form – they had done so to take on the shape of their creators after all. What if they had somehow got into the city and taken on Teyla's identity? He hadn't even thought of that. What of Teyla was lying injured somewhere, in need of his help?

'I have to go find her,' he suddenly announced, pushing up from the desk and swaying with the change in position.

Rodney caught his arm, but let go the minute he felt it was safe to do so, looking embarrassed about the contact. 'Who? Teyla? Why would you want to go find her? You think she cracked you round the head earlier!'

'I just need to figure something out,' he muttered heading out into the corridor.

Walking as fast as he could, he had to catch himself against the wall several times to steady himself so he didn't crumple. His brain really wasn't ready for his body to stay vertical yet, so vertical while moving at a slow jog was even less acceptable. The walls seemed to undulate around him as if Atlantis were breathing...more like struggling for breath he realised as he saw the erratic shifts going on around him. The city was suffering...it was being attacked; he could feel its fight to survive as surely as if it was his own battle. Perhaps it was...or perhaps he was finally losing his mind after all.

He stopped to take a few breaths, struggling himself now to successfully inflate his lungs. Was the city pulling him down with it? No, that was ridiculous. A lot of his thoughts recently had bordered on insanity...the freaky nightmares, the city communicating with him, seeing dead doctors in his dreams...maybe he had imagined all this stuff with Teyla. He briefly considered heading back to the infirmary and turning himself in, even turned around to head in the right direction, but then decided against it. He had to find Teyla. He wouldn't settle until he knew she wasn't some kind of evil Replicator twin.

Forging ahead, he'd only managed a few more shaky paces when he heard a voice shout out from behind him.

'What're you doing out of the infirmary?'

Ronon. Thank God – someone who could help him. He turned around, reaching out to steady himself against the wall. 'You know me; I always was a lousy patient,' he quipped, throwing his friend a crooked smile.

'Keller says I have to bring you back. You're in no condition to be wandering around on your own,' Ronon told him, unsmiling.

'Look, I just want to go apologise to Teyla, then I promise to go back to the infirmary. Okay?'

Ronon pulled his energy gun from his thigh holster and aimed it at him.

'Easy, Chewie!' Sheppard gasped, raising his free hand in surrender. 'I just said I'd go back with you in a few minutes. Don't you think you're over-reacting?'

Ronon remained as inscrutable as ever, his eyes locked onto Sheppard's.

'Oh c'mon, buddy. Five minutes is all I need. You can gimme that, right? You can even come with me if you wanna be sure I don't go back on my word.'

A flash of pure hatred lit Ronon's eyes, the same one he'd seen crossed Teyla's dark orbs, and the one he'd first seen in his dream.

'Not you, too,' he breathed, backing up a few steps and wondering if there was any way he could outrun the Satedan.

The bolt of energy the gun fired in his direction answered that question before he could even try.