'Can you hear something?' the Doctor asked.

38.Miranda could, right on the edge of her hearing, like the sound when you first turn a television on or blow on a dog whistle. This wasn't a continuous tone, more a series of bleeps and blips.

'Is it Morse code?'

The Doctor concentrated for a couple of seconds. 'No,' he concluded. 'It's a regular pattern, though. We need to get in there.'

The Doctor and Miranda walked all the way round the building, but there wasn't a gate.

'Perhaps we missed a bit,' Miranda said, but the Doctor pointed to their tracks in the snow.

He was examining the wall. Miranda turned her attention to the ground.

The Doctor's Trabant wasn't the only thing that had left tracks in the snow.

There was a set of footprints that came up from the main road, and led off to the left.

'Dad, look at the snow.'

'Not really the best time for that, Mir,' he called back.

Miranda pulled a face at him, and followed the trail. There were several sets of prints, all converging at the same point on the wall. It wasn't a gate, though it just looked like bricks. A big lump of snow had drifted up nearby, as though it was covering something. Miranda stepped towards it.

A hand grabbed her shoulder.

It was the Doctor.

'No,' he said.

'OK,' she replied. 'Do you see the prints?'

They led right up to the wall. The Doctor bent over to take a closer look at them. 'Small shoes. More your size than mine. Boys and girls.'

He placed his hand on the wall, but it was solid.

'There's a hidden door. How did they open it? Oh, of course.'

He took the phone from his pocket and waved it towards the wall. There was clicking sound, then the wall swirled away like water down a plughole.

'Phased molecules,' the Doctor said knowledgeably.

He stepped through. The wall swirled back up into place behind him.

'Dad!' Miranda shouted.

'I can't get it to open again,' he told her, glad she was on the other side. 'Go back to the car.'

Miranda, sulkily, agreed. She was sitting back in the pa.s.senger seat before she realised he could have thrown the phone over the wall to her, and by then she knew it would be too late to go back and get him.

The Doctor made a beeline for the radio mast. It must have been a hundred feet tall. It would be able to broadcast over a wide area hundreds of square 39 miles, at a guess. He'd never seen an aerial with this exact configuration before. There were plenty of footprints in the snow, leading to a small building at the base of the mast.

Before going to the mast, he took a peek through a window in one of the main factory buildings, where a light was on. Sitting at a wide workbench were a dozen boys, all working to construct telephone handsets with blank-faced determination. They made a miniature production line, nimbly taking a component from the tray in front of them, fitting it into place, then pa.s.sing it to the boy on their right. The last boy dropped the handsets into a large black bag, overseen by a small red-haired girl. It all happened in perfect unison.

None of them was speaking.

The Doctor took a closer look at the girl. Her telephone was clamped to her ear. Now, he saw that all the boys had handsets over their right ears, as if they were glued there.

He tapped at the window. As he suspected, not one of the children even looked up.

He made his way round to the smaller building at the base of the radio mast, keeping in the shadows. It was a more recent structure, like a Portakabin, constructed from the same metal as the mast. There were no windows, but there was a door that opened when the Doctor tried it.

He found a single room, lined with computer banks. Three girls around Miranda's age sat at control stations, all of them staring at screens. They didn't react to the Doctor's arrival. They sat playing with their phones, thumbs hooked around them, pressing the b.u.t.tons almost instinctively. As the Doctor watched he could see that they were compiling machine codes. Endless lines of letters and numbers were being displayed on the screens in front of them.

He recognised one of the girls as Rachel Rowley, a cla.s.smate of Miranda's.

Then the monitors cleared, and a new message flashed up.

UPLINK READY.

'XLNT:-)' the girls said with one voice, sounding disconcertingly like a church congregation.

The Doctor pushed one of them out of the way to get a better look at the screen.

CONNECTING.

'W8! Who R U? >:-('

The Doctor looked around curiously. The girls' voice had no trace of p.u.b.erty, but it did have a slight electronic warble. It reminded the Doctor of a couple of the seances he'd attended in the 1920s the girls were possessed. But what was doing this?

'I am the Doctor,' he told the girls gently.

'Dr? Dr??' came the confused reply.

40.'Indeed.'

The Doctor hesitated. He decided to pick on the girl he recognised. 'And you're Rachel, aren't you?'

'nt rachL n e more we r d Netwk'

'The Network?' the Doctor echoed. He thought for a moment, then snapped his fingers. 'Intelligent software that runs on a human brain instead of a computer. Self-replicating telecommunications technology. It was only a matter of time.'

'u knO of us'

'Not specifically. But already the telephone network of this planet has as many individual connections as there are neurons in the human brain. It's only one step from that to behaving like a brain.'

'Y D age of orgnic lfe is over 2moro b lgs 2 us :-)'

'But you're not of this Earth, R U? I mean. . . Are you?'

'N. We hve Xisted 4x10(2d8) yrs. Netwk Coverage will b universal.'

'Broadcast from one planet to another, spreading out in irresistible wave-fronts at the speed of light, picked up by any planet with sufficiently advanced technology. Ingenious.'

The Doctor moved around the control stations, trying to work it out.

'So those are the ends, but what are the means?'

He glanced at the cables. There was the mast outside. Why children? Every screen was flashing the same message: CONNECTING.

'You're just the advance party, though, aren't you? You're going to try to receive a signal from s.p.a.ce. Then what?'

'N1 cn stop us not evn U Dr :-)'

'You're probably right. So if you'd just explain your plan to me, omitting no detail?'

'N'

'Are you sure?'

'Y'

'Fair enough. No harm in asking. Saves a bit of time, that's all. Right, I'll have to work it out for myself.'

An instrument was confusing him. A Geiger counter. The Doctor recoiled.

'Children's brains are more susceptible to radiation than adult brains. Mind control via radiation emissions. Total mental domination of the human population.'

'UR > clver thn U :dr'

'Do you mind if I. . . ?'

The Doctor grabbed Rachel, pushed her off her chair, took her place, s.n.a.t.c.hed the phone from her and started working at the controls.

41.Rachel picked herself up, grabbed the Doctor's wrist and squeezed so hard he had to let the phone go. He tried to pull away, pushing his wrists down between her thumb and fingers, the weakest point of any grip. But he could barely move his hand.

'And you are stronger than you look,' the Doctor noted ruefully. She threw him across the room.

'Limin8 d dr :-)'

W8!!.

The great booming voice seemed to come from high above them. The Doctor looked around, trying to identify the exact source.

'Y Gr8 Provider?' the three girls chorused, without looking up from their phones.

d Dr s kwn 2 me of old. We hve f0 aX time & spce. He has of10 cut us off :-) off :-) 'You know me?' the Doctor asked.

Y.

'And you call yourself the Great Provider?'

Y.

'I don't remember you, I'm afraid.'

d dr hs gr8 knwledge. We s%d + his memries 2 our d8abase.

'Oh, I don't really have memories. I've misplaced them somewhere. A long story, at least I a.s.sume it is. How can I explain this to you? Well, I suppose you could say that my memory tapes have been wiped.'

d dr tries 2 DCve us. Attach d h&s free headset.

'If d dr tries 2 resist :-(?'

normal terms & conditions apply.

The Doctor tried to stand up, but two of the girls put their hands on his shoulders and forced him back down.

The third girl was bringing over a pair of chunky silver headphones. She clamped them over the Doctor's ears. He could hear a screech, then a high-pitched burble. A string of digital information, he realised.

'Calling,' the Doctor said. 'Connecting. . . '

He could feel a new presence. It was as though his brain had swallowed iced water and he could feel it working its way around. A mind of extraordinary clarity that divided the universe into binary states. Yes or no, to every question. Quite unlike an organic mind.

The intruder vanished from his brain.

The Doctor grinned.

W8!.

'What's the problem, O Great Provider?'

42.Now it was the Doctor's turn. His mind surged down the headset, into the computers then out to the boys' and girls' handsets. As he ran through the electric labyrinth of the printed circuits, he carefully shut down the Great Provider's mind, dismantling and deleting it. The Provider had run a simple set of instructions to each of the children. The Doctor undid every one of them, line by line.

CONNECTION FAILING. SIGNAL LOST. NO CARRIER.

'Don't call us, we'll call you,' the Doctor shouted up at the ceiling.

The girls had collapsed on the floor, their phones melting as though they'd been dipped in acid. He'd have to call the police and get their parents to take them home. The computers were sparking and fizzing, their tapes unspooling and fraying. The mast was silent.

The Doctor headed out, back to Miranda and the car. She was waiting for him at a new gap in the wall. She ran over to hug him.

Behind them, the mast disintegrated in a ma.s.s of blue sparks. 'What did you do?' Miranda asked.

'The person behind this wanted the contents of my brain. But my mind is. . .

Well, let's just say there's more to it than meets the eye.'

'He's gone?'