Strike rose early on Tuesday morning. After showering, putting on his prosthesis and dressing, he filled a thermos with dark brown tea, took the sandwiches he had made the previous evening out of the fridge, stowed them in a carrier bag along with two packets of Club biscuits, chewing gum and a few bags of salt and vinegar crisps, then headed out into the sunrise and off to the garage where he kept his BMW. He had an appointment for a haircut at half past twelve, with Jimmy Knight’s ex-wife, in Manchester.

Once settled in the car, his bag of provisions within easy reach, Strike pulled on the trainers he kept in the car, which gave his fake foot better purchase on the brake. He then took out his mobile and began to compose a text to Robin.

Starting with the names that Wardle had given him, Strike had spent much of Monday researching, as best as he could, the two children the policemen had told him had vanished from the Oxfordshire area twenty years previously. Wardle had misspelled the boy’s first name, which had cost Strike time, but Strike had finally dug out archived press reports about Imamu Ibrahim, in which Imamu’s mother had asserted that her estranged husband had kidnapped the boy and taken him to Algeria. Strike had finally dredged up two lines about Imamu and his mother on the website of an organization that worked to resolve international custody issues. From this, Strike had to conclude that Imamu had been found alive and well with his father.

The fate of Suki Lewis, the twelve-year-old runaway from a care home, was more mysterious. Strike had finally discovered an image of her, buried in an old news story. Suki had vanished from her residential care home in Swindon in 1992 and Strike could find no other mention of her since. Her blurry picture showed a rather toothy, undersized child, fine-featured, with short dark hair.

Little girl it was, but after they said it was a little boy.

So a vulnerable, androgynous child might have disappeared off the face of the earth around the same time, and in the approximate area, that Billy Knight claimed to have witnessed the strangling of a boy-girl.

In the car, he composed a text to Robin.

The dirt on his windscreen shimmered and blurred in the rising sun as he left London. Driving was no longer the pleasure it had once been. Strike could not afford a specially adapted vehicle, and even though it was an automatic, the operation of the BMW’s pedals remained challenging with his prosthesis. In challenging conditions, he sometimes reverted to operating brake and accelerator with his left foot.

When he finally joined the M6, Strike hoped to settle in at sixty miles an hour, but some arsehole in a Vauxhall Corsa decided to tailgate him.

“Fucking overtake,” growled Strike. He was not minded to alter his own speed, having settled in comfortably without needing to use his false foot more than was necessary, and for a while he glowered into his rearview mirror until the Vauxhall driver got the hint and took himself off.

Relaxing to the degree that was ever possible behind the wheel these days, Strike wound down the window to admit the fine, fresh summer’s day and allowed his thoughts to return to Billy and the missing Suki Lewis.

She wouldn’t let me dig, he had said in the office, compulsively tapping his nose and his chest, but she’d let you.

Who, Strike wondered, was “she”? Perhaps the new owner of Steda Cottage? They might well object to Billy asking to dig up flowerbeds in search of bodies.

After feeling around with his left hand inside his provisions bag, extracting and ripping open a bag of crisps with his teeth, Strike reminded himself for the umpteenth time that Billy’s whole story might be a chimera. Suki Lewis could be anywhere. Not every lost child was dead. Perhaps Suki, too, had been stolen away by an errant parent. Twenty years previously, in the infancy of the internet, imperfect communication between regional police forces could be exploited by those wishing to reinvent themselves or others. And even if Suki was no longer alive, there was nothing to suggest that she had been strangled, let alone that Billy Knight had witnessed it. Most people would surely conclude that this was a case of much smoke, but no fire.

Chewing crisps by the handful, Strike reflected that whenever it came to a question of what “most people” would think, he usually envisaged his half-sister Lucy, the only one of his seven half-siblings with whom he had shared his chaotic and peripatetic childhood. To him, Lucy represented the acme of all that was conventional and unimaginative, even though they had both grown up on intimate terms with the macabre, the dangerous and the frightening.

Before Lucy had gone to live permanently with their aunt and uncle in Cornwall, at the age of fourteen, their mother had hauled her and Strike from squat to commune to rented flat to friend’s floor, rarely remaining in the same place more than six months, exposing her children to a parade of eccentric, damaged and addicted human beings along the way. Right hand on the wheel, left hand now groping around for biscuits, Strike recalled some of the nightmarish spectacles that he and Lucy had witnessed as children: the psychotic youth fighting an invisible devil in a basement flat in Shoreditch, the teenager literally being whipped at a quasi-mystical commune in Norfolk (still, for Strike’s money, the worst place that Leda had ever taken them) and Shayla, one of the most fragile of Leda’s friends and a part-time prostitute, sobbing about the brain damage inflicted on her toddler son by a violent boyfriend.

That unpredictable and sometimes terrifying childhood had left Lucy with a craving for stability and conformity. Married to a quantity surveyor whom Strike disliked, with three sons he barely knew, she would probably dismiss Billy’s story of the strangled boy-girl as the product of a broken mind, sweeping it swiftly away into the corner with all the other things she could not bear to think about. Lucy needed to pretend that violence and strangeness had vanished into a past as dead as their mother; that with Leda gone, life was unshakably secure.

Strike understood. Profoundly different though they were, often though she exasperated him, he loved Lucy. Nevertheless, he could not help comparing her with Robin as he bowled towards Manchester. Robin had grown up in what seemed to Strike the very epitome of middle-class stability, but she was courageous in a way that Lucy was not. Both women had been touched by violence and sadism. Lucy had reacted by burying herself where she hoped it would never reach her again; Robin, by facing it almost daily, investigating and resolving other crimes and traumas, driven to do so by the same impulse to actively disentangle complications and disinter truths that Strike recognized in himself.

As the sun climbed higher, still dappling the grubby windscreen, he experienced a powerful regret that she wasn’t here with him now. She was the best person he had ever met to run a theory past. She’d unscrew the thermos for him and pour him tea. We’d have a laugh.

They had slipped back into their old bantering ways a couple of times lately, since Billy had entered the office with a story troubling enough to break down the reserve that had, over a year, hardened into a permanent impediment to their friendship… or whatever it was, thought Strike, and for a moment or two he felt her again in his arms on the stairs, breathed in the scent of white roses and of the perfume that hung around the office when Robin was at her desk…

With a kind of mental grimace, he reached for another cigarette, lit up and forced his mind towards Manchester, and the line of questioning he intended to take with Dawn Clancy, who, for five years, had been Mrs. Jimmy Knight.