Sir Anthony filled them in on what he had discovered as the Doctor poured more tea.

'I took this cottage,' he explained. 'Lucky to find it.

Getting the generator and so on installed was a bit tricky. Had to do it in secret.'

'Everyone knows,' Peri told him. 'They told us down at the pub.'

Sir Anthony looked crestfallen. 'I thought I'd managed that bit quite nicely. Oh well. Do they know about David Madsen as well?'

'Madsen? What about him?' the Doctor asked as he settled back into his seat.

'Not sure really. But his predecessor was an old duffer who suddenly got offered a partnership in Harley Street for no very good reason. Completely unmerited, I'm told. Madsen was the only applicant to take his place. His form arrived the day after the advertis.e.m.e.nt and he could start at once.'

'Convenient,' Peri commented.

'Indeed. So whatever it is, I reckon he's in on it. Sheldon arrived back here at about the same time, if you want the clincher.'

'Still supposition,' the Doctor said. 'But it does give us something to start with. Perhaps we'll have a quiet word with Dr David Madsen. He was over at Sheldon's Folly yesterday.

He could well be involved.'

'I saw him at lunchtime,' Peri offered. 'He seemed a bit distracted. Worried about something.'

'Well, if I was in his shoes,' Sir Anthony said, 'I don't know which I'd be more worried about - that my patients die, or that they don't seem to stay dead.'

The ceiling was a white void above him. For a while he just lay there, staring up at it, as he did when he woke in the mornings. Nothing odd. Nothing odd at all. Except...

He sat up suddenly, eyes wide. He wasn't dead. He was awake. Awake and alive. Dave Madsen looked at the bedside cabinet, suddenly wondering if the whole thing was a dream.

A nightmare. All of it.

Several white tablets were scattered across the top of the cabinet. An empty gla.s.s tumbler stood in the middle of them, angled drunkenly because it was on top of one of the tablets.

On the floor by the cabinet was an empty whisky bottle, lying on its side.

And he didn't even have a hangover. No ill effects at all.

'Oh no,' he murmured as he rubbed his eyes. 'Oh my G.o.d, no.' It was already too late. Too late to resolve anything, too late to help Liz. Too late to die. It wouldn't let him, not like this. Not so easily.

'Logan Packwood.' Sir Anthony nodded. 'Another geneticist, like Sheldon, although he started in computer science of course. Actually,' he went on, 'Janet Spillsbury has some background in genetics, though as I said her main role was with the s.p.a.ce Agency.'

'So what are they all doing here?' Peri asked.

'And how do we find out?' the Doctor added.

'Well,' Sir Anthony offered, 'I was thinking, before you two showed up, that I might call Madge.'

'Madge.' The Doctor nodded. 'Good idea. Who is Madge?'

'My PA at the ministry. She's still there, though I don't think she's quite as important to the new regime as she used to be. But we're friends.' He pulled his mobile phone from his jacket pocket and switched it on. 'The problem is getting a signal. The coverage here isn't really very good. Comes and goes a bit. Sometimes nothing, and sometimes it'll work even in the cellar, clear as a bell.' He looked at the readout on the phone for a while, then smiled. 'Ah,' he said. 'Looks like we could be in luck.' He pressed a speed dial b.u.t.ton. 'So long as it doesn't cut out on us.'

'Don't tell her anything you don't have to,' the Doctor warned. 'You never know who might be listening, or who she might talk to.'

Sir Anthony nodded. 'Understood. That's a.s.suming she's there.'

'What do you think, Doctor?' Peri asked quietly as Sir Anthony listened to the phone, waiting for an answer.

'I'm not sure. Not yet. But I don't like it.' Sir Anthony was talking quietly into the phone now. 'I don't like it at all,'

the Doctor finished.

'That's right, Madge,' Sir Anthony was saying. 'I'm on Dorsill...Oh, not too bad. Coping. The fresh air does me good I'm sure. Look, I was going to pop over and see young Sheldon while I'm here. Silly not to. Just remind me what he's working on, would you? So I know what planet he's on. You know what he's like.'

He listened for a while. The Doctor and Peri watched expectantly, but there was nothing in Sir Anthony's expression to give them a clue as to what Madge was telling him.

'Really?' he said after a while. 'That secret, eh?

Interesting. But you must have some idea...' He listened again for a while, his eyebrows slowly rising.

He used the knife for chopping vegetables and he kept it sharp.

Madsen held it up for a moment, letting the afternoon sunlight streaming in through the kitchen window glint on the blade.

He had never noticed before how the sharp edge of the blade was scratched and pitted where the sharpener had ground it away. The wooden handle was warm in his sweaty hand. He had already rolled his sleeves up.

A couple of times Madsen had dealt with attempted suicides. One of those was slashed wrists. But like most people the girl had a.s.sumed you ran a hot bath and then cut across the wrist. Not the best way, Madsen considered clinically as he stared at his own wrist. He could see the pale blue veins running up to his palm. Cut across and you would hit the bone well before you severed anything major. No, far more effective to slice up the wrist, along the line of the veins and arteries.

He pressed the point of the knife into the pale skin. He could barely feel the p.r.i.c.k as it broke through. One advantage at least to all this. Just one. A bead of blood welled up at the point of the knife. He was breathing heavily now as he angled the blade, pushed it in deeper, then sliced it along his wrist.

A thin line of red followed in the wake of the knife. Then it filled out as the blood bubbled up and ran over his wrist. It splashed to the floor. As the blade met the artery, the thick red liquid started to squirt upwards. He knew it was going to happen, but he was still surprised at the force of his heart as it pumped the lifeblood out of his arm.

He smiled, a thin bloodless smile of satisfaction, as he continued to drag the knife through his flesh. Mercifully, there was still no pain. And then, suddenly, the flow of blood slowed. It was already getting sticky, congealing. Madsen pulled out the knife - it made a sucking sound as it came. The line of red was already fading. The blood along his arm was a flaky crust of dark brownish red.

The knife clattered to the floor as he stared in disbelief at his arm. The flow of blood had dried up completely now. He tore at the wound with his fingernails, getting flakes of blood under them. Rubbing the dry blood away like rust.

Beneath it his arm was slowly revealed. There wasn't even a scar. He was holding the wrist, cradling it in his other hand, staring at it transfixed as he slowly crumpled to the floor. The blood was congealing into a sticky mess round his knees as he rocked back and forth. His sobs echoed round the kitchen.

The sun was already low in the sky, though the day was still bright. The Doctor had suggested that Sir Anthony fill them in on what he had learned as they walked. He thought that whatever that might be, a return visit to Sheldon's Folly was called for. Sir Anthony led the way.

'I have a boat pulled up in the next cove,' he said. 'Do a bit of fishing. Rod and line, not nets, you know. It's easier to beach it in the next bay.'

'So, are we any the wiser?'

'A little. Madge doesn't know what Sheldon is working on. It's cla.s.sified on the computer system. She had a look for me while we were talking, found she didn't have access. That miffed her a bit, I don't mind telling you.'

'So we don't know?' Peri asked.

'Well, she said she did overhear mention of Sheldon's work during some meeting or other the other week. Nothing helpful, though.'

'Anything might help,' the Doctor said. 'However insignificant it may seem.'

Sir Anthony paused to indicate with his walking stick which way they were going. The path was narrow with brambles on one side and the edge of the cliff on the other.

'We go down this fork here. It takes us down the side of the cliff and brings us out in the bay. Not far.' They had to walk in single file. The Doctor led the way, Peri came last. They were all watching their footing carefully as they made their way down the steepening track.

'She said,' Sir Anthony continued as they walked, 'that someone mentioned the "experiment" in relation to Sheldon, though they didn't say anything specific.'

'Pity,' the Doctor said.

'There was some talk about genetic material, whatever that might mean. Oh, and someone was talking about "Gatherer Three", but that may not be related.'

The Doctor stopped so suddenly that Sir Anthony almost collided with him. 'European s.p.a.ce Agency, did you say?' he demanded without looking back.

'What? Oh, yes. Janet Spillsbury, that's right.'

'Then it means that Gatherer Three is certainly related,'

the Doctor told him He started slowly down the slope again.

'And it also means that things are rather more serious than I had thought.'

'Do I have to ask out loud,' Peri called from behind them, 'or are you going to tell me?'

'Sorry, my dear.' Sir Anthony picked his way carefully after the Doctor. 'Gatherer Three was a s.p.a.ce probe. The Gatherer programme was a joint NASA/ESA project. NASA provided the launch facilities since Ariane wasn't cutting it for this sort of payload. The European s.p.a.ce Agency, in particular Britain and specifically my old department, handled the material.'

'And he means material,' the Doctor called back. 'Don't you, Sir Anthony?'

'Wasn't really involved myself, you understand, though it was under my jurisdiction. But yes. After two prototype trials, the European s.p.a.ce Agency succeeded in launching a deep s.p.a.ce probe like no other. Gatherer Three was supposed to travel into the far reaches of our solar system. And then return.'

'As I recall,' the Doctor explained, 'its mission was to skim close to the outer planets and their moons, navigate through the rings of Saturn and the asteroid belt, and then its elliptical orbit would bring it back close enough to Earth for a NASA shuttle to intercept it.' He was almost at the bottom of the cliff now. The beach below was a ma.s.s of shingle. 'Isn't that right, Sir Anthony?'

'Well, essentially, yes. Though I'm surprised you know about it. Cla.s.sified, you know.'

'That wouldn't stop him,' Peri said. 'So when does this s.p.a.ce probe go up?'

The Doctor stopped as he reached the bottom of the steep slope. He reached back to help Sir Anthony down the last few feet. 'I think it's already been, Peri,' he said. 'I think that's the point.'

She joined them on the beach, her feet sinking into the shingle. 'You mean, it brought something back.'

'Not that I had heard,' Sir Anthony told them. 'I was still in charge back then. They were examining the samples - each is sealed until it's a.n.a.lysed under controlled conditions.'

'So what did it bring back?'

'Rock, ice, that sort of thing. Boring to you and me, but fascinating to the boffins. Very valuable stuff, I'm told. They examine each sample, then a.s.sign it to the expert in that field within the department for further a.n.a.lysis. Then the expert can decide whether to involve others from their field.'

The Doctor was wading across the shingle. In the distance they could see a small rowing boat pulled high up the beach.

The sound of the waves on the shingle was a soothing rhythm as they struggled towards it, feet slipping and sliding through the pebbles.

'So what would have to be inside one of the sealed sample containers for Sheldon to be called in as an expert?' the Doctor asked.

'Well, given his pet project and area of expertise was the DNA computer,' Sir Anthony said, 'I suppose some sort of genetic material.' He paused in mid-step. 'Oh, I say,' he murmured.

'Genetic material,' Peri repeated. 'You mean, as in life form?'

Old Jim lived in a small cottage behind the main village street.

He could sit on the back step and look out over the moors. He could see the top of the church spire above the other houses, and even the edge of the quay. He loved to just sit and watch the sea, and he loved to wander over the moors with his pipe firmly clenched between his old teeth. His other pa.s.sions were fishing, though he rarely went out with the youngsters in the boats now, and shooting. But he hardly ever picked up a gun.

Everyone knew he had a shotgun - most people knew he kept it locked in a cabinet in his tiny living room.

The only reason for the padlock was that once, in the 1960s, a policeman from the mainland had checked his licence and reminded him that really he should keep the gun under lock and key. The padlock and the clasp it now hung from had arrived on the next mail boat.

Old Jim was out walking the moors when Dave Madsen came for the gun.

Most people in Dorsill never locked their doors. There was no need, and it was inconvenient if others could not just drop by when they wanted or needed. Jim was no exception, and Dave Madsen let himself into the cottage. He called out, but there was no reply. He checked outside the back door to see if Old Jim was sitting watching the world go by. There was no one.

The cabinet was made of old wood. The padlock was strong, but the cabinet itself was not. It did not take Madsen long to wrench the doors from the front of it, leaving splintered wood hanging from the rusted hinges. He pulled out the shotgun, broke it and stuffed in two cartridges. He knew next to nothing about guns. But he did know which way the cartridges went, and which end of the shotgun did what. He hadn't realised there were two triggers, but that made sense.

He understood how that worked. And to be absolutely sure, after he pushed the barrels of the gun into his mouth, he pressed hard on both the triggers.

The sound was deafening in the tiny room. Enough to crack the back window. The fine hairline appeared across the grimy gla.s.s a moment before it was splattered red.

The only sound after the echo died away was the body slumping to the ground.

The Doctor had sat down on a bank of shingle and was throwing pebbles as hard as he could out into the sea. Peri was sitting next to him, her knees drawn up under her chin. Sir Anthony preferred, he said, to stand. His stick was pushed into the stony beach and he was leaning on it.

'So how does this explain the walking dead?' Peri wanted to know.

The Doctor threw a stone, watched it arc through the sky.

'If alien genetic material had been introduced into the body...'

He paused to watch the pebble splash into the crest of a nascent wave. 'Perhaps that's what the experiment is.'

'How would that work then?' Sir Anthony asked.

'No idea.' The Doctor threw another stone. 'But if we're talking about some sort of - what? Symbiont? Something that lives within the human body, feeds off it.'

'Like a parasite?' Peri asked.

'Yes, but a mutual parasitism. The material gets something from its host. Maybe just a warm place to live.'

'Ugh.' Peri wrinkled her nose is distaste.