Appeals to the general public stirred mixed feelings in Warren. For every serious response there might be no shortage of time wasters, unbalanced attention seekers who handed themselves in under false pretences. It could be unnerving to watch them re-enact their fantasy crimes, watch them give it their all as they made an impossible firearm out of thumb, middle finger and index; rammed would-be blades into all the wrong places; curled their fingers and strangled the air until they were red in the face. How crestfallen they looked when told they were free to go.

So the prospect of being roped into their audience, of having to sit through these people’s palaver, their nonsense, shortened a temper that, in Warren, was longer than most. But it was all part of the job, you got used to it more or less, the hassle quickly forgiven if the appeal helped to bring some new detail to light. For a week now he’d felt as though he were working in the dark.

Instead of answers he was uncovering more and more questions. ‘I’m appealing for anyone who knew Jasbir to come forward.’ But how many had known Jasbir really?

He’d gone to the dead man’s workplace and spoken with the men at their machines. Jasbir had been a good worker, they said. They’d had no complaints. He had never been heard to say a bad word about anyone.

No sharp tool had been reported missing.

He’d gone to the pubs and spoken to the regulars, showing the picture to refresh memories. The Jasbir in the picture looked rather abashed at all the attention.

He’d asked about Jasbir’s demeanour on the night in question, and in the evenings leading up to it, whether he had said anything, been seen with anyone, perhaps been bought a round of drinks, but the regulars just looked up from their pints and shrugged, dunno, no, sorry, can’t help you, and whatever he’d said or done no one seemed to care to recall.

The barmen, too, shook their heads and wiped their hands with their towels. He’d had a few, as usual, was their recollection. He hadn’t been one for confidences.

✲

From both sides of his family Warren had carried on something special that went back generations. His father’s side had bequeathed him ‘Warren’ which had once been his grandmother’s name, that is, her maiden name, then his father’s middle name before becoming his own. On his mother’s side, several relatives had been seen as eccentric and keepers of their own company, and Warren would tell me he assumed his autism had come down from them.

There was his mother’s cousin, whom he’d called ‘Uncle’ and who had made his career as an Egyptologist. He remembered the thick bushy beard that hid half this solitary uncle’s face and the tanned sinewy arms from digs in distant lands, but even more so the endless erudition as the man talked stelae and sarcophagi with his cousin’s eight-year-old son. By the age of nine Warren had been taught – much to his delight – to decipher hieroglyphs.

He was thinking also of two sisters of his grandmother Williams, the grandmother who wasn’t Warren, great-aunts who had dealt in antiquities and lived out in the middle of nowhere, far away in the countryside. Of these great-aunts, and his summer stays with them as a child, Warren had retained fond and vivid memories.

‘Here’s 50p for you,’ one or another of these old sisters would say when Warren was down to his last few pence in pocket money, bending and handing him the shiny seven-sided coin whose value they still reckoned inwardly in shillings. With that coin weighting the pocket of his shorts Warren would go and buy himself a paper bagful of sweets, then wander off over the fields feeling as prosperous as must do millionaires.

He wandered to his heart’s content, wandered high and low over the hilly miles, left entirely to his own devices. He could have vanished ten times over before either sister would have thought to look for him.

One of the great-aunts kept horses and lived with a pet sheep, Horace, close to the ruins of an ancient estate, its buildings long gone to seed and overgrown with thick roots and branches. It was little wonder that she preferred to walk Horace further afield, on flatter ground, occasionally stopping to give it digestive biscuits. Warren, on the other hand, loved investigating those ruins – there wasn’t a nook or cranny he wouldn’t visit to appease his curiosity. Halls that were shells of their former selves, a tower without any of its floors. High above him, the cawing of ravens. He stepped through gaping arched doorways, pressing a palm to the mossy stone walls as he peered out from the glassless windows. However long and often he toured these grounds he never once killed time there; always he found something to occupy his mind. Always the scattered shards of some pot or saucer to reconstruct. A date or inscription for him to piece together. A remnant of some porcelain plate he might hold up to the light and admire for many minutes – a tribute to the beauty of its floral motifs.

The other great-aunt had bought an old lodge and given it over to her collection. For tens of years she had been collecting every kind of doll that she could purchase. Hundreds of dolls crammed into every inch and corner of the downstairs rooms, but lined up and labelled along shelves and in smart display cases.

‘See this one, Warren?’ this great-aunt would push her thick glasses up her nose and point at one of the cases. ‘Made of wax, from around 1810. A pedlar.’

Some were English, some were Continental. Others were Russian. They were all different shapes and sizes. One stood tall and leggy, another small and round; this doll had a Victorian bonnet, that doll wore a petticoat.

On a hot day their owner wore a sari. She was the older of the two sisters, born in 1915, and gave next to no thought to appearances. But she was doll house-proud.

Warren levelled his gaze at the miniature furniture – teensy chairs and tables laden with cut-out foods, microscopic cupboards that opened on crockery and drawers on cutlery, inch-high grandfather clocks and made beds and baths and hat stands. A tiny walnut bookcase containing even tinier books containing the complete works of Shakespeare.

Only the fact that he could never play with any of these toys, could touch them with his eyes but not with his sticky fingers, lightly adulterated his pleasure. But he handled each of them firmly in his mind and, years later, whenever he imagined the solution to a crime, he wondered if what he saw – the little figures and objects set against various backdrops in his mind’s eye – wasn’t like some tragic scene out of his great-aunt’s collection.

✲

Warren loosened his scarf as he turned onto Salisbury Road. He walked up the path to one of the houses and when he reached the door the occupant answered and let him in. The man – he was in his early forties and bald – continued to stand expectantly even after Warren had stepped into the narrow hallway. Then he offered Warren tea or coffee and they sat in the front room.

The dead man’s former schoolmate, Jagdev Rai, said that maybe his old friend had kept bad company, he didn’t know, he had never pried into that side of his life. He and Jasbir went way back, that was correct, but even so Jasbir didn’t tell him everything.

Jasbir had been over to the house several times in the past year, Rai said. To have a bath and a warm bite to eat and a proper kip. His wife and kids liked him. Everyone liked Jasbir. He was easy-going and charming. You couldn’t help liking him.

Did Jasbir have a key to the house? Warren wondered. No. It was always better to be around. There was the outdoor, you know, the off-licence, a few doors away. Though the family couldn’t always be at home. Jasbir would call or text in advance. In case Rai had a wedding somewhere – he was a caterer. Otherwise Jasbir would pop over of an evening and when he was tired he’d go and kip in the van. The white van parked behind the house. He preferred that to the settee. More private. And he could leave when he pleased.

Warren asked about Canada – a possible new lead turned up by his team’s inquiries. Wanting to make a fresh start, the dead man had emigrated in 2006. He had some relatives in Canada. But about a year ago, towards the end of 2011, Jasbir had returned. Apparently his return to the UK was unexpected. Had he got himself in hot water over there? Might he have been running away from something, or from somebody?

Rai said he didn’t know anything about that. Jasbir had never talked to him about Canada.

Of course the detective could have a look inside the van.

Warren followed Rai round the house and sighted the Mercedes-Benz Sprinter. First generation. When had Jasbir last kipped in there?

Rai thought for a moment as he unlocked the van. The twenty-sixth. November twenty-sixth. The night before Jasbir had stayed in the room above the pub, and left in the early hours for the park. The night before his last.

Where Jasbir had slept a dusty blanket lay rumpled on the passenger seat. Warren thought he could make out the faint impression left by the man whose sleep was now eternal.

✲

The present would be nothing without the past, Warren has always known. He has known it from as far back as he can remember. He is both a man of his time – and of another time, more so as he has grown older. In his social media posts, which began in 2013, photos of his horse riding – a rare way to stay in the here and now – alternate with retweets of BBC Archive clips, ‘on this day’ memorials, snippets of jumpy home movies featuring cars, and black-and-white photos of bygone cityscapes.

Warren is old enough to recall the thrill that was riding the 90 bus towards the suburbs of Birmingham. He’d take a top-deck seat right at the front and fidget until the approach to Camp Hill. His fellow schoolboys and the older teens, in the surrounding rows, grew equally tense and quiet. And then it appeared, in the near distance: The Camp Hill flyover. A narrow, shuddery ramp across a busy junction, prefabricated in steel and concrete. The bus would pick up speed as it climbed into the sky, your breathing went on pause, the tops of buildings blurring until they disappeared. You felt the rise and the dip in the pit of your stomach; it was like being astride a giant racehorse.

How was such an experience possible in the middle of an otherwise flat city, Warren’s ever-enquiring mind wanted to learn. When had this particular section of road been erected and why? It had to have a history – a sequence of events, now invisible, which had forged what people presently saw, and it astonished him that in perceiving this he was rather unusual. The ramp spanned many metres and several decades. For children of Warren’s age, and older, the Camp Hill flyover had always been there. They assumed it was a road, just a road, like any other.

Warren’s father had long encouraged his son’s frequent questions, his interrogating nature, and he was quick to say that Warren was right. Things are never only as they appear. Because something is doesn’t mean it always was. What his classmates all viewed as a permanent fixture had once been the epitome of temporary constructions. Engineers had put it up one weekend in 1961 as a stopgap cure for traffic jams.

Perhaps they had forgotten to take it down. Perhaps they had forgotten they’d ever put it up.

✲

It was January 2013 and the police investigation into Jasbir’s death had slowed. Canada was hardly next door. By the middle of the month the West Midlands sky looked like snow. Residents took salt and shovels to the roads and pavements. The lake in the park froze and thawed and in February froze again.

The events of the evening and night of 27 to 28 November remained a mystery, every avenue of the inquiry seeming to go nowhere. Every time Warren and his team thought they were getting warmer their leads fell through. Impossible to ascertain the whereabouts of the dead man’s mobile phone, or the sharp instrument that had ended his life. The police would have revisited the scenario of suicide but for the fact that no such instrument had been found at the scene.

No knife at the scene. No farewell note left anywhere either. No history of previous suicide attempts or even of depression. No hesitation marks on the dead man’s throat. That Warren should mentally rehearse all these points spoke to the sombre mood in his team. If any of his overworked colleagues was thinking of moving on, who could blame them? And it was also true that, in his final months, Jasbir’s position had become parlous, not to say desperate. Warren and his team were learning just how parlous from their inquiries. For years he had been borrowing money from family and friends; he was thousands of pounds in debt.

On the snowiest days Warren and his team reviewed CCTV recordings of the hours preceding Jasbir’s death. Seven hundred hours of tape taken from forty-six locations around the area. It would take a person one whole month non-stop to view all the footage, two if they blinked, three if they ate and slept – so Warren’s colleagues focused their attention on the time and sites closest to the incident. They watched and watched and watched the sleeping streets that circled the park, and they did not see anyone running, or even walking, away.

As for Warren, he was never out of patience and he watched one tape in particular, rewinding and pausing, rewinding a little more, then a little bit more again …

✲

Our lives are lived forwards but understood backwards.

This thought, and others like it, came to Warren as he wandered in a churchyard in Bromsgrove. Certain free days, he liked nothing better than to drive over there and read the gravestones. The oldest had been weathered near illegible, but he would stop and crouch, brush away the dirt and moss and recover a name, an age, a date of death, occasionally, a brief tale – clues to a prior existence that had otherwise vanished without a trace.

On one stone he read:

TO THE MEMORY OF THOMAS SCAIFE.

Late an Engineer on the Birmingham and Gloucester Railway who lost his life at Bromsgrove Station by the Explosion of an Engine Boiler on Tuesday the 10th of November 1840.