On the far side of the wall he heard the whine of an angle-grinder. Building work was going on to extend the mortuary.

The greyness of the day outside was grimly matched by the atmosphere in here. Grey light diffused through the opaque windows. Grey tiled walls. Brown and grey speckled tiles on the floor that were a close match to the colour of a dead human brain. Apart from the blue surgical gowns worn by everyone in here, and the green plastic aprons of the mortuary staff and the pathologist, the only colour in the whole room was the bright pink disinfectant in the upended plastic dispenser by the washbasin.

The post-mortem room reeked, permanently and unpleasantly, of Jeyes Fluid and Trigene disinfectant – sometimes compounded by the stomach-churning, freshly unblocked-drain stench that came from opened-up cadavers.

As always with a Home Office post-mortem, the room was crowded. In addition to himself, Nadiuska and Cleo, there were Darren Wallace, the Assistant Mortuary Technician, a young man of twenty-one who had started life as a butcher’s apprentice; Michael Forman, a serious, intense man in his mid-thirties, who was the Coroner’s Officer; James Gartrell, the burly forensic photographer; and a queasy-looking Glenn Branson, who was standing some distance back. Grace had observed several times in the past that, despite the Detective Sergeant’s big, tough frame, he always had a problem at post-mortems.

Unknown Male’s flesh was a waxy off-white. It was the colour Roy Grace had long associated with bodies in which the life forces had ceased, but on which decomposition had not yet begun to present, to the naked eye at least, its hideous processes. The winter weather and the cold of the seawater would have helped to delay the onset, but it was clear that Unknown Male had not been dead for long.

Nadiuska De Sancha, her red hair clipped up, tortoiseshell glasses perched on her finely sculpted nose, estimated that death had probably occurred four or five days ago – but she was not able to get closer than that. Nor was she able to establish, for the moment at any rate, the precise cause of death, largely on account of the fact that Unknown Male was short of most of his vital organs.

He was a good-looking young man, with close-cropped, downy black hair, a Roman nose and brown eyes that were fixed open. His body was lean and bony – but from undernourishment rather than exercise, Grace judged from the lack of muscle tone. His genitals were modestly covered by the fleshy triangle of skin from his sternum, which had been removed and placed there by Nadiuska, as if to afford him some dignity in death. The flesh of his chest and stomach, either side of the massive incision running down his midriff, was clamped back, revealing a startlingly hollow ribcage, with the intestines, like shiny, translucent rope, coiled beneath.

On the wall to their left was a chart for listing the weight of the brain, lungs, heart, liver, kidneys and spleen of each cadaver examined in here. There was a dash against each item, except for the brain, the only vital organ the cadaver still possessed, and very likely to be the only one that would go to his grave with him.

The pathologist removed his bladder, laid it on the metal dissecting tray, which was on raised legs above the cadaver’s thighs, then made one sharp incision to open it. She carefully bottled and sealed samples of the fluid that poured out, for tests.

‘What’s your assessment so far?’ Grace asked her.

‘Well,’ she said, in her exquisite broken English, ‘the cause of death is not absolute at this moment, Roy. There’s no petechial haemorrhaging to indicate suffocation or drowning, and with the absence of his lungs I can’t say for sure at this point if he was dead prior to immersion. But I think we can surmise, from the fact that his organs were removed, that was pretty likely.’

‘Not many surgeons operate underwater,’ Michael Forman quipped.

‘I don’t have much to go on from the stomach contents,’ she continued. ‘Most of it has been dissolved by the digestion process, although that slows post-mortem. But there are some particles of what looks like chicken, potato and broccoli – so that indicates he was capable of eating a proper meal in the hours preceding death. That is not really consistent with his absence of organs.’

‘In what way?’ Grace asked, conscious of the inquisitive eyes of the Coroner’s Officer and Glenn Branson.

‘Well,’ she said, and waved her scalpel down his opened midriff. ‘This is the kind of incision a surgeon would make if he was harvesting organs from a donor. All the internal organs have been surgically excised, by someone experienced. Consistent with this is the fact that the blood vessels have all been tied off with sutures before being cut through to remove the organs.’ She pointed. ‘The perinephric fat that would have been around the kidneys – the suet, if you are a cook – has been opened with a blade.’

Grace reminded himself not to eat suet for a long time to come.

‘So,’ Nadiuska continued, ‘all this would indicate that he was an organ donor. Now, what directs me even more towards this possibility is the presence of these external indications of medical intervention.’ She pointed again. ‘A needle mark in the back of the hand.’ She gestured at the neck. ‘A puncture mark.’ Then she pointed at the right elbow. ‘Another puncture mark in the antecubital fosse. These are consistent with the insertion of cannulae for drips and drugs.’

Then, taking a small torch, she gently levered open the dead man’s mouth with her gloved fingers and shone the beam in. ‘If you look closely you can see reddening and ulceration to the inside of the windpipe, just below the voice box, which would have been caused by the balloon inflated on the end of the endotracheal ventilator tube.’

Grace nodded. ‘But he ate a meal of solids – he couldn’t have done that with an endotracheal tube, right?’

‘Absolutely right, Roy,’ she said. ‘I don’t understand this.’

‘Perhaps he was an organ donor who was subsequently buried at sea, and then carried by currents away from the burial zone?’ Glenn Branson suggested.

The pathologist pursed her lips. ‘It’s a possibility. Yes,’ she concurred. ‘But the majority of organ donors tend to be on life support for a period of time, during which they would be intubated and on intravenous drip feeds. It is odd to me that there is undigested food in his stomach. When I do the tox screen, that may show up muscle relaxants and other drugs that would be used for the removal of organs for transplant.’

‘Can you give me an approximation of how many hours from when he had eaten until he died?

‘From the state of the food, four to six at maximum.’

‘Couldn’t he have died suddenly?’ Grace asked. ‘A heart attack, or a car – or maybe motorbike – accident?’

‘He doesn’t have injuries consistent with a serious accident, Roy. He has no head or brain trauma. A heart attack or an asthma attack is a possibility, but considering his age – late teens – both, I would say, are a little improbable. I think we could be looking for some other cause.’

‘Such as?’ Grace scribbled a sudden note on his pad, thinking of something that would need following up.

‘I can’t speculate at this stage. Hopefully lab tests will tell us something. If we could get his identity, that might help us also.’

‘We’re working on that,’ he said.

‘I’m sure it is the lab tests that will provide the key. I think it is very unlikely that the tapings are going to produce anything, as he wasn’t in waterproof wrapping,’ the pathologist went on. Then she paused briefly, before adding, ‘There is one other thought. This food in the stomach. In the UK, because there is no automatic organ harvesting without consent, it does often take many hours from brain death for consent to be obtained from next of kin. But in countries where there is just an opt-out, like Austria and Spain, then the process can be much quicker. So it is possible that this man is from one of those countries.’