Ianto was unconscious. Luckily (or at least the Doctor considered it lucky, Jack wasn't so easily convinced) Ianto hadn't actually disappeared. Physically anyway. The shields within the TARDIS were enough to protect Ianto, but whatever was taking the kids had slipped past the mental barriers and stolen the Welshman's mind. Motor functions were still working, and Ianto's body was still supporting itself, but there were practically no brainwaves. He wasn't even a vegetable. It was like someone had pulled out his soul.

"Ok, so… tell me again," Jack sighed exasperatedly, rubbing the bridge of his nose with his thumb and fore finger. "Exactly how is this helping us?"

"New symptom," the Doctor said, examining the brainwaves and scans he'd printed out closely, his glasses perched on his nose. "It narrows down the alien activity to roughly… forty two."

"Species?" Jack asked, though he didn't sound too hopeful.

"Uhhh… no…" the Doctor shook his head. "Forty two thousand planets."

"Fantastic," Jack sat down in a swivel chair and pulled the files towards him again in the vain hope that they'd missed something important.

"Well don't sit there," the Doctor threw a few brain scans at him. "There's no point in re-reading them, you might as well examine these instead."

"Doctor, of all the things I'm good at, I'm not exactly an expert in neurology," Jack snapped, rather more harshly than he meant to.

"Well you'll need this as well then," the Doctor chucked a huge tome at Jack's head.

Jack caught it just before it hit him and began flicking through the pages in search of in depth picture of the human brain, glancing up occasionally to shoot glares at the Doctor.

"I'm going to actually try and bring him back," the Doctor continued pulling out a syringe, needle and small vial of amber coloured liquid. He attached the needle and pulled some of the liquid into the syringe.

"What is that?" Jack asked.

"Something to help boost his acetylcholine production," the Doctor replied, injecting into the IV tube.

"Wait… hang on, that's the chemical that helps with memory," Jack frowned.

"Yeah, of which he has none, this will boost it, and hopefully, if whatever alien is doing this to Ianto has some physical connection within his brain, it'll combat it and your boyfriend won't be a vegetable," the Doctor spoke as though he was talking to a three year old.

"He's not my boyfriend," Jack said quietly. "Not anymore. I don't think he's going to forgive me for what happened."

The Doctor softened slightly then. It was stressful for all of them. This was why he hadn't wanted another companion after Rose. He wasn't sure he'd be able to cope if he lost someone else.

"Look, I'll do everything I can," he said, taking the large neurology book out of Jack's hand and finding the right page for him. "I promise I will get back the man you loved."

"Doctor," Jack shot him a look.

"Ok… I will try," the Doctor amended. "You know I will."

"Yeah…" Jack nodded. He knew the Doctor wouldn't let anyone else go through the pain of losing a loved one if he could do something to stop it.

It was a long night and the Doctor was no closer to finding an answer. He just didn't have enough information. Half way through the next morning he threw down his scans and sat with his head in his hands, thinking hard.

Jack knew this was a bad sign. The Doctor always found something to go on, he always had an idea or a lead or something. But these aliens, whoever they were, just weren't giving him anything.

"Maybe…" Jack paused as he hovered over the Doctor. "Maybe if words trigger it, numbers reverse it?"

He was desperate. It was a shot in the dark. Jack had only thought of it because he'd been pondering the lockdown that Suzie had initiated. There was no reason for it to work; there was no reason for the Doctor to run with it. But they had nothing else.

The Doctor looked up at him for a moment frowning. He looked away and started pulling the brain scans back towards him, marking places and muttering to himself.

"Seven…" he frowned and stood up quickly, moving past Jack and pulling up some of the records on the computer, flicking through any that had medical notes. There were only four who'd had brain scans, but they all showed similar readings. "Seven…"

Jack stared at him completely bemused.

"What's seven?" He asked.

The Doctor looked up and grinned.

"Jack you've done it!" He grabbed the Captain and pulled him in for a kiss. "You are a genius and don't ever let me tell you otherwise!"

"Uhh… ok…" Jack smiled still confused.

"Seven… think about it Jack!" The Doctor held up seven fingers. "How many senses do you have?"

"Well… five," Jack replied. "Touch, taste, sight, smell and hearing."

"Exactly, but the average alien has seven," the Doctor counted them off. "The human five, then memory perception and telekinesis."

"With you so far," Jack nodded.

"Obviously I have eleven, because being a Time Lord, I'm much better at-" The Doctor stopped as he caught the look Jack was shooting him. "So anyway, these kids, Ianto, they all have seven markers, like codes that tell me which part of the brain controls what."

"Wait, how can they have seven?" Jack asked.

"All humans are born with the ability to have the seven, but you lot hardly ever use your brains, you've got nothing to stimulate the last two senses. Kids though, until they hit a certain age, still retain the function to activate these senses. And Ianto, well Ianto had low level psychic training… and I'm guessing he can't have been more than nineteen when he did it."

Jack shrugged.

"So the aliens are playing off these senses!" The Doctor grinned pleased with himself. "Don't you see?! It narrows it down because only two species in the galaxy have the ability to invade minds like this. The Finos and the Juklags!"

"Umm… so now we know that..?"

"We can solve this! We can bring everyone back! We can save the day!" The Doctor stood as if waiting for applause.

"What about those mental patients? One of them was fifty two," Jack replied.

The Doctor wilted instantly.

"We're still missing something…"