Rose was a few doors away, huddled up on a bed in the dark. The TV screen in her room had been smashed. She greeted the Doctor with a smile and a 'Hi', but neither reached as far as her eyes.

He was with her in two strides, a.s.suring her that he was who he appeared to be and that she was safe now.

'You found the monsters, then?' she asked, forcing herself to sound cheerful but not quite succeeding.

'Oh yeah.' He tapped a forefinger against her temple. 'They're in here.'

Rose flushed. 'What's that s'posed to mean?'

The Doctor moved the finger to his own head. 'They're in here too. Microorganisms in the air of this world. The settlers' equipment isn't sensitive enough to detect them and it's been a long time since they looked anyway.'

'Which means... what? We're all just breathing 'em in?'

The Doctor grinned. 'Yeah. Hold on, here comes the science bit. These organisms feed off electrical activity in the atmosphere. They were probably quite happy till human beings came here and offered them something a bit tastier.'

'You mean our... brains? They're eating our brains?'

'Er, not quite. Just absorbing their neuroelectrochemical signals. The right side of the adult human brain has the best flavour, apparently. It's like sugar to them. They've become quite the addicts, started colonising wholesale in there.' He tapped Rose's temple again. 'Trouble is, too much rightbrain activity dreams, for example and they get bloated. The surplus impulses are reflected back where they came from, creating a feedback loop.' He was twirling his fingers in a hopeless attempt to demonstrate. 'The dreamer finds his dreams amplified over and over again until the right brain reacts to them as if they're real and communicates that information ' he clasped his hands together and described an arc through the air 'to the left brain.'

'Left brain,' repeated Rose, still not quite following.

'Yeah. Logic, reasoning, language, all that stuff. And memory.'

'So that's why they... they kind of half froze my brain...'

'So you couldn't dream, yeah.'

'All the muscles down my lefthand side...'

'Right side of the brain controls the left side of the body.'

'But you can make it better can't you?'

'Once we get to the TARDIS, yeah. I can flush the microorganisms right out of your system. Till then ...'

Rose's face fell.

'You can get through this!' said the Doctor. 'If the people of this world can learn to live with it well, most of the time I know you can. You know what the monsters are now, Rose. You can fight them.'

'Did... did Jack tell you...'

'That you tried to break into the Big White House cos you thought I told you to? Nope, didn't need to. I read your note at the hotel.'

Rose avoided his gaze. 'You must think I'm pretty thick.'

'Not your fault.'

'Seeing things that aren't there, though.'

'Not your fault.'

'And it's like... like even after after I knew what was wrong with me, yeah, I kept... We were letting the patients out, and the orderlies didn't know what had hit them. I thought they were gonna tear some of 'em apart. There were people running and screaming and fighting, and it was like... I didn't know how much of it was real and how much...'

'Not your fault.'

'Doctor... You know last night, in the ... when I said you were "mental"...'

'I know,' he said gently. 'Tell me something: was I clever?'

The question threw Rose. 'Eh?'

'When I brought you here. Was I clever?'

'You weren't... I mean, he he wasn't...' wasn't...'

'Real. I know, yeah. But was I clever? That version of me, in your head was I resourceful and witty and charming and handsome?'

For the first time, a hint of a smile a genuine smile broke through her awkwardness. 'Bit full of yourself, aren't you?'

'Bit full of your yourself.'

'I don't get it.'

'Pat yourself on the back, Rose Tyler cos all that cleverness and resourcefulness and that wit and that charm, it came from inside you.'

'And the handsome?'

'Well...' said the Doctor, with a modest shrug.

And Rose remembered how to laugh.

Cal Tyko looked up as the Doctor entered his dorm. Recognition flickered in his eyes and was joined by hope until he saw the two patients standing guard at his visitor's shoulder, and fear took over.

He scrambled off the bed and backed up to the wall, his eyes wide. The Doctor wondered what nightmares he was seeing.

'Cal Tyko,' he said with a tight smile. 'Got something for you.'

'What... what are you going to do to me?' gasped Tyko, trembling, finding his voice at last.

'What, you don't wanna take your own medicine? It's for your own good. You look fantasy crazy to me. Don't you want to get better?'

'I was just... just doing my job. Just trying to help people.'

'Yeah, me and you both, mate.' The Doctor found a crumpled piece of paper in his pocket and threw it at Tyko with contempt. 'Difference is, I don't lobotomise them in the process. Here! A few ideas about what's causing your problem. The rest's up to you. Unless you want things to stay like this for ever.'

'You're asking me to... to...'

'To take a leap of faith, yeah. Scary, isn't it!'

Then the Doctor turned and breezed out, not looking back to see if Tyko had reached for the balledup paper.

He had a great deal more still to do.

At the far end of the third floor from the lifts, the Doctor found an office like the one in which Tyko had left him and Waller that morning: desk, chairs, computer, screens over two walls, no windows. It had been overrun by inmates, but he quickly shooed them out.

He sat at the computer, took a few seconds to familiarise himself with its operating system, then opened its Ethernet connection. Within minutes, he had found his way through several backdoors and three firewalls to a server that had not been used for decades and yet, as he'd hoped, had never actually been dismantled. A server that had belonged to the old government.

'Um... Doctor?'

He'd been aware of Domnic's presence for a while; he had just been ignoring him. His eyes remained fixed on the monitor, his fingers a blur on the keyboard.

'These... these microorganisms. You said they'd come back.'

'Yeah. They're already swimming up your nose, through your mouth, down your ears. Won't be long before there are enough of them in your brain to start the delusions all over again.'

'But you can drive them out again, right?'

'Could. Won't be here.'

'I... see.' Domnic sounded disappointed, but he made no move to leave.

For a minute or so there was silence. Then the Doctor gave up his work in exasperation. 'There's something else, isn't there? There's always something else.'

'I... I've been watching TV in one of the patients' dorms.'

'Well, good for you,' he said scathingly. 'Life pretty much back to normal for you already, eh?'

'I was looking for Static. I thought... you know, with everything going on, I thought it'd still be... I can't find it, Doctor. I can't find it on any frequency.'

'Oh, is that all?' said the Doctor. 'Doesn't exist.'

Domnic's jaw trembled. 'You... you mean...'

'Static. Hal Gryden. All fiction. Any more questions?'

'How...'

He came into the room proper and sank into the spare chair. He looked sh.e.l.lshocked and it occurred to the Doctor that he'd been a bit brusque. He'd related the bare facts without considering the effect they might have. Domnic had suspected the truth already but still, its confirmation had dashed his hopes. And on Colony World 4378976.DeltaFour, hope was hard enough to come by.

'I saw you in the hotel room, remember?' he said, more kindly. 'You said you were watching Static. You were more right than you knew.'

'Then the revolution, everything he said... All lies. Nothing's gonna change.'

'Yeah, it will. Gryden might not be real, but he's the next best thing. He's an urban legend. Everyone believes in him and on this world that makes makes him real. Even the newspapers and the TV news are talking about him. You saw the infoscreens on our way in here. Your revolution's started, with or without its figurehead.' him real. Even the newspapers and the TV news are talking about him. You saw the infoscreens on our way in here. Your revolution's started, with or without its figurehead.'

'Fantastic!'

'No,' said the Doctor, 'not "fantastic". Very, very far from "fantastic" cos this world doesn't need a revolution. There's no one to revolt against. All you can do is tear yourselves apart and, believe me, that ball's already started to roll. Soon, no one will be able to stop it. If I can't find a way to save this world p.r.o.nto, there won't be much of a world left to save.'

It took Domnic some time to come up with a reaction to that, and then all he could manage was, 'Oh.'

'Camera,' said the Doctor abruptly. Apparently, that wasn't enough, so he explained, 'I need a video camera. There are plenty around. In every dorm, behind the telly. Or the ones in the corridors might be easier to get hold of. Get a couple of the patients to help you. They're used to obeying anyone who shows the slightest authority.'

He'd already returned to his work when he realised that Domnic was still sitting there dumbly and that maybe even 'the slightest authority' was too much to ask of him. 'Go and see Captain Jack,' he sighed. 'He'll find a few pairs of hands for you. Go on, then, quick as you like!'

The camera was set up on a makeshift tripod constructed from three chairs, its lens trained on the desk. Its innards were hanging out, trailing wires to the computer, and in the middle of this lashup sat the Doctor's sonic screwdriver, glowing with blue light. The Doctor himself was running from computer to camera to screwdriver, checking connections, taking readings here, making adjustments there and explaining his plan to the audience he had somehow acquired.

'Best way to save this world,' he said, 'is to use its most powerful weapon.'

'What's that?' asked Domnic.

'It's the media, isn't it?' said Rose. 'The telly.'

'Gold star,' said the Doctor, taking her by the shoulders and moving her gently but firmly out of his way. 'There are thirtysix TV channels serving this planet, but they all bounce their signals off the same satellite which I've just located. Amazing what you can find on the Net these days.'

Jack frowned. 'You mean to cut in on all all those channels?' those channels?'

'No point in doing half a job.'

Rose grinned as she clarified matters to the watching patients: 'He's seen this on Batman Batman. It's how the villains always deliver their ransom demands to Gotham City.'

'This part of the building this block it's steelreinforced concrete,' Jack mused. 'You could use its framework as an aerial.'

'Yup.'

'But to blanket all frequencies, you'd have to send a broadspectrum transmission.'

'Yup.'

'Does the sonic screwdriver have enough power for that?'

'Nope.'

'No?' echoed Domnic in dismay.

The Doctor dropped into his chair at the computer and started typing again. 'Had a better idea. When this world had a government, they set up an emergency distress channel overrides the signals to all other channels in the event of a global disaster: riots, wars, invasions, monsters, that kind of thing.'

Jack nodded in admiration. 'So you crack the frequency of the government distress signal, then we only need a narrowband transmission to activate the override.'

'And you can do that?' asked Domnic.

'It's protected by a series of pa.s.s codes,' said the Doctor, 'but I've knocked together a little program that should see to that in about...' He smiled as the computer pinged and the screen lit up with the data he needed.

'So, you're gonna talk to the world,' said Rose. 'What are you gonna say?'