He got his first coffee of the day and started on those they had signalled as worth further attention, though even of these at least half seemed to him of little use or relevance. But the others – maybe fifteen shots – he saved in a new file, to look at more closely. He also copied the whole team in on them.

Three looked of certain interest. The first was a shot of Rosemary Poole in the entrance to her bungalow, looking out, but with her hand on the door as if she was about to close it. The light was poor, the shot obviously taken late in the afternoon. He enlarged it by 200 per cent. It went completely out of focus. 150 per cent . . . not much better. At 75 per cent he could see Mrs Poole’s face more clearly. She looked as if she had been saying something to a person just ahead. Perhaps she was greeting them, perhaps saying goodbye.

The next was the rear of a white van with the number plate, all but the last digit, clearly visible.

The third was of the grass outside the bungalows, frosted over but also struck by a shaft of thin wintry sunlight. A shadow – no, not a full shadow, maybe half or two-thirds of one – lay across the grass. It was almost certainly the shadow of a person, but he could not tell much more.

At nine fifteen, Simon had the whole team in the CID room. The photos were up on the screen.

‘Keep looking at them,’ Simon said. ‘Get the images in your head. Nobby Parks was hanging around the D of C houses at all hours, usually after dark. He took these pics at random – he was playing with his toy without a clue how to use it. But there’ll be something on these . . . some detail, some link . . . it won’t hit you in the face – if it did you’d have got it. But there’ll be something.’

He filled them in on the files Nathan had brought down. ‘The case is out there – HOLMES, court proceedings, national and local papers. Won’t take you more than an hour to bring yourselves completely up to speed with Alan Frederick Keyes and the Yorkshire murders which are blow-by-blow the exact same as ours here. Only difference, there were three elderly victims up there, we only have two and let’s make sure it stays that way. I want everything you can find about this man Keyes – everything in Yorkshire, before and after the murders and the trial, but more importantly since then. That’s ten years. Search our force’s database – all the forensics, CRIMIN, every sort of local and area record. I want to know where he’s living, what he’s doing. This is now our number-one suspect. I want him found. I want him brought in. When he’s here, I want him grilled until his ears smoke. But we’ve got to catch him first. Local records, electoral register, council tax lists, register of marriages . . . Link anything you find with the info I’ve given you from the file. It’s on your computer now, code name ‘BarleyMow’. Keep it there. If you strike gold and find any sort of photograph, bring it to me. But I don’t just want his picture. I want him.’

Forty-five

LONDON. HE WOULD never want to live here again but for an occasional day there was nothing to beat it and he always returned home feeling reinvented, ready to raise the stakes, challenge himself all over again, both in work and as an artist. Why it had this effect of a quick inhalation of pure oxygen Serrailler could never quite suss out but it hadn’t failed him and he knew it wouldn’t fail him now. He stopped his cab at the top of the Mall. It was cold but the sun was bright. There had been a state visit a few days previously and the flags were still out. He walked down the wide paths, past St James’s Palace, past Clarence House, and turned to climb the steps into Carlton House Terrace when there was the sound of massed hooves coming at a spanking pace up the Mall towards him. The Household Cavalry, jingling and sparkling, plumes swaying, went past to the occasional tourist’s camera and wave, lifting his heart. As a small boy he had longed to be one of those guardsmen looking resplendent on their way to Buckingham Palace, or escorting the Queen’s state coach or carriage. He remembered with a smile holding a silver-painted wooden sword, riding the arm of the sofa throughout Trooping the Colour.

He was meeting Joel Winslow, now a professor, at his club. Winslow had been his lecturer on the two profiling courses he had taken, and had even tried, without success, to persuade Simon to divert his career that way. They had forged a bond and Simon had gone to him for an opinion about peculiar or difficult cases once or twice before. Winslow would not be proud of him for making such a basic error after the murder of Elinor Sanders.

‘Always bear the alternative in mind,’ he said now, as they sat in the bar before going in to lunch. ‘This isn’t an exact science, Simon. I seem to remember trying to impress that on you.’

‘You did. I’m doing more than kick myself.’

‘Don’t bother. In general, you were right. Your man was more than likely to wait a few weeks or even much longer before he killed a second time. Your only mistake was in upgrading a “likely” to a “definite” and calling off the patrols.’

‘I didn’t call them off. I halved them – and some.’

They were sitting at the end of the bar, a comfortable room adjacent to the entrance hall. Serrailler had been to this club a few times and enjoyed the excellent food and the handsome rooms, some small and intimate, others vast, formal and rather intimidating, with high ceilings and huge portraits on the walls. The dining room was wood-panelled with tables well separated, so that private conversations were perfectly possible. He wouldn’t like to belong to one of these places, though his father loved it, but he could enjoy the surroundings and also be amused by the people. Club members out of central casting, he thought, as two entered the bar now. Pinstripes, stiff collars, plum-coloured faces.

‘From what you’ve told me, it’s pretty clear that the second killing was out of necessity rather than choice.’

‘He got the wind up.’

‘The old lady saw him or heard him, or else he thought she had. He couldn’t take the risk. But he still killed in the same meticulously organised way, he was very much in control. No panic, no mistakes, even if he was in a hurry. He’s a cool customer, this one. Anything else you can tell me?’

Over their excellent, entirely traditional lunch – potted shrimps, rare beef from the trolley, cheese, a bottle of the house claret – Simon went over the killings again, stressing the trademarks and telling him the confidential secrets that had been kept from the press and the public.

‘Give me a portrait of your killer,’ Joel said, ‘see if I agree.’

‘Psychopath. Sadist. Ritualist.’

Joel nodded, his mouth full of Yorkshire pudding and gravy.

‘Loner.’

‘Not necessarily. Loner inside himself certainly – but he could live a perfectly ordinary life otherwise. He won’t want to draw attention to himself in the normal course of things. He can blend in.’

Simon described Nobby Parks but after only a few sentences Joel shook his head.

‘This man is highly organised, neat and tidy, folds his clothes. And he isn’t so stupid as to wander about the area in which he operates, at night, being seen, having patrol cars take him home. Rule him out – well, the usual 99 per cent anyway. You always leave a crack to let yourself back in, but I put money on it not being this Nobby Parks.’

‘Grudge against old women.’

‘Possibly, yes. Had an elderly female relative who treated him badly when he was a child. He could have been brought up by her – a grandmother, an older aunt. He hated her, and more than likely, that was because she humiliated him. He’s getting his own back for that – he’s humiliating his victims. Making them sit in front of a mirror, cutting their toenails. I wonder if he was made to do that for this old relative when he was a boy?’

‘Or she could have cut his, and he felt ashamed or embarrassed.’

‘So this would be a way of getting his own back.’

‘What sort of age?’

‘More difficult. Somewhere between thirty and fifty? He’s still physically strong and he’s fit.’

‘You don’t have to be that strong to kill an eighty-year-old woman. Could “he” be a “she”?’

‘Possibly.’

‘But if this is a twisted sort of vengeance on the old woman relative, why does he – or she – need to go on killing? Isn’t one enough? He’s had his revenge.’

‘It’s satisfying – the first time, he felt a terrific high. So far as he was concerned, he’d got his own back, even if it wasn’t actually on the same woman. But after a while, it started eating into him again. And, he’d enjoyed it. That’s the other key. He likes killing. He likes the way he does it. He likes to humiliate.’

The cheeseboard was not over-elaborate. A half-truckle of Cheddar. Stilton. A creamy white Cheshire. Nothing foreign, nothing runny. Classic, Simon thought, as a slice of Cheddar was laid reverently on his plate. The celery was in a proper celery jar. There were no other embellishments.

‘And he keeps trophies. They usually do. Sometimes they cut a lock of hair. Quite a few sadistic killers of younger women, prostitutes and so on, have been known to take pubic hair. In this case it might be nail clippings. He may collect newspaper reports of his murders and when the police get something wrong he’ll gloat. Or he could keep it all on a computer. If he lives with someone, wife or girl or boyfriend, that’s easier to conceal. He knows his way round. Round the police system, round houses, especially this sort. Round the town. This is night-time but there’s always somebody about – a late taxi, a police patrol, someone walking home from a late shift or a club, someone taking a dog for a last pee – so he won’t march prominently down the main roads, he’ll take short cuts and alleyways and know his way round back gardens and across rough ground.’

‘Local then.’

‘Oh yes.’

Simon had not mentioned the Alan Keyes case files to Joel and, on the spur of the moment, decided to keep them to himself for the time being.

They drank coffee sitting on the sort of library armchairs in which old men fell asleep. One or two were already doing so, newspapers sliding gently onto their laps. The coffee was the only thing with which he could find fault. It was filter, it was bitter, and it was not hot enough.

Time he got back home.

‘Anything else you want to run past me, call,’ Joel said as they parted on the flight of marble steps that led to the door.

‘It helps to see the picture a bit more clearly. Thank you.’

‘You need to catch him sooner rather than later. You’re the DCS, I don’t want to teach my grandmother to suck eggs, but he’ll do it again, Simon.’

They parted and Simon walked down Piccadilly to his gallery off Albermarle Street. It was some time since his last exhibition and he had a conversation about plans for the next, probably in May of the following year. He looked round the current show of paintings which were not greatly to his taste, went down Burlington Arcade and bought Rachel a violet cashmere shawl and Cat a box of her favourite dark chocolate gingers, before heading for the train. As it pulled out, the late-afternoon sky was dark and a drizzle had set in. He had had the best of the London day.

He sat in a quiet carriage with his iPad, and in the light of what Joel had said, he sent an email to the team urging them on, stressing that the killer could strike again, and another asking for an all-night uniform guard at the sheltered houses and extra patrol cars in the area. There were two men and two women in residence now, but the rest of Duchess of Cornwall Close was still empty, although every bungalow was spoken for. Understandably, people were reluctant to move in until the killer was caught and, understandably, the council was also putting pressure on CID.

Simon closed the screen down and was about to open the paper when someone tapped him on the shoulder.

‘Say if you would rather not be seen with me.’ The Chief Constable, in her London suit and with a laptop bag, had been looking for a better seat. ‘I mean it, Simon.’

‘Don’t be silly.’ He indicated the one opposite to him.

‘Not going to talk work, or anything else much, I’ve got a load of stuff to read. I have been wondering if you’ve thought over what I said the other day though.’

The job. He had not thought about it once since asking Nathan for his opinion.

‘I have. It’s not for me. I need to be hands-on – but you knew that already.’

Paula Devenish looked at him steadily. ‘Yes. I’m not surprised, though I wish you felt otherwise.’

‘No you don’t. Nor does the force. It needs a very different sort of person. Actually, it’s got what it needs already. You’re not going to change your mind?’

She shook her head. ‘We all hate change,’ she said, opening her laptop. ‘But we also need the shake-up we get along with it.’

They did not speak again until the train was drawing into Bevham Station, where the Chief’s car had just pulled up at the forecourt entrance. Simon’s was stowed away in the multi-storey opposite.

He appreciated the fact that she had not harangued him about the murders, though she would be as concerned as he was to make progress. She had not taken advantage of having him trapped in a seat opposite her. She delegated. She trusted. She knew when to leave someone to get on with their job.

He was going to miss her.

Forty-six

NONE OF THE team spoke in answer to Serrailler’s question. He looked around, puzzled.

‘What’s going on here?’

After a second, Ben said, ‘I think it means just that, guv. There’s nothing going on. Nobody’s found a single thing. We’ve all come up against a sort of hole in the ground.’

‘Into which this Alan Keyes fell.’

They all piped up.

‘Nothing in the electoral rolls, nothing in any of the civil registers . . . he hasn’t married, had children or died.’

‘Nothing in employment records.’

‘I’ve been onto every employer large and small. No one’s taken on a builder of that name, permanent or temp, in the last ten years.’

‘What’s the radius?’

‘Employment – fifty miles of here, guv.’

‘But civil registers, guv – we’re talking nationwide. I’ve done a full trawl.’

‘Prisons? Mental institutions?’

Heads were shaken.

‘Like I said – he’s dropped down a big black hole, guv. It’s like he just ceased to exist.’

Simon stood up and banged his hand on the table. ‘That’s it. Got it.’