After a minute spent stretching and scratching his armpits while his eyes acclimatized to the odd shapes rising on all sides in the gloom of Joan and Ted’s sitting room, he Googled Margot Bamborough for a second time and, after a cursory examination of the picture of the smiling, wavy-haired doctor with widely spaced eyes, he scrolled through the results until he found a mention of her on a website devoted to serial killers. Here he found a long article punctuated with pictures of Dennis Creed at various ages, from pretty, curly-haired blond toddler all the way through to the police mugshot of a slender man with a weak, sensual mouth and large, square glasses.

Strike then turned to an online bookstore, where he found an account of the serial killer’s life, published in 1985 and titled The Demon of Paradise Park. It had been written by a well-respected -investigative journalist, now dead. Creed’s nondescript face appeared in color on the cover, superimposed over ghostly black and white images of the seven women he was known to have tortured and killed. Margot Bamborough’s face wasn’t among them. Strike ordered the second-hand book, which cost ￡1, to be delivered to the office.

He returned his phone to its charging lead, put on his prosthetic leg, picked up his cigarettes and lighter, navigated around a rickety nest of tables with a vase of dried flowers on it and, being careful not to nudge any of the ornamental plates off the wall, passed through the doorway and down three steep steps into the kitchen. The lino, which had been there since his childhood, was icy cold on his remaining foot.

After making himself a mug of tea, he let himself out of the back door, still clad in nothing but boxers and a T-shirt, there to enjoy the cool of early morning, leaning up against the wall of the house, breathing in salt-laden air between puffs on his cigarette, and thinking about vanished mothers. Many times over the past ten days had his thoughts turned to Leda, a woman as different to Joan as the moon to the sun.

“Have you tried smoking yet, Cormy?” she’d once asked vaguely, out of a haze of blue smoke of her own creation. “It isn’t good for you, but God, I love it.”

People sometimes asked why social services never got involved with Leda Strike’s family. The answer was that Leda had never stayed still long enough to present a stable target. Often her children remained in a school for mere weeks before a new enthusiasm seized her, and off they went, to a new city, a new squat, crashing on her friends’ floors or, occasionally, renting. The only people who knew what was going on, and who might have contacted social services, were Ted and Joan, the one fixed point in the children’s lives, but whether because Ted feared damaging the relationship between himself and his wayward sister, or because Joan worried that the children might not forgive her, they’d never done so.

One of the most vivid memories of Strike’s childhood was also one of the rare occasions he could remember crying, when Leda had made an unannounced return, six weeks into Strike’s first term at St. Mawes Primary School. Amazed and angry that such definitive steps as enrolling him in school had been taken in her absence, she’d ushered him and his sister directly onto the ferry, promising them all manner of treats up in London. Strike had bawled, trying to explain to her that he and Dave Polworth had been going to explore smugglers’ caves at the weekend, caves that might well have had no existence except in Dave’s imagination, but which were no less real to Strike for that.

“You’ll see the caves,” Leda had promised, plying him with sweets once they were on the train to London. “You’ll see what’s-his-name soon, I promise.”

“Dave,” Strike had sobbed, “he’s called D-Dave.”

Don’t think about it, Strike told himself, and he lit a second cigarette from the tip of his first.

“Stick, you’ll catch your death, out there in boxers!”

He looked around. His sister was standing in the doorway, wrapped in a woolen dressing gown and wearing sheepskin slippers. They were physically so unalike that people struggled to believe that they were related, let alone half-siblings. Lucy was small, blonde and pink-faced, and greatly resembled her father, a musician not quite as famous as Strike’s, but far more interested in maintaining contact with his offspring.

“Morning,” he said, but she’d already disappeared, returning with his trousers, sweatshirt, shoes and socks.

“Luce, it’s not cold—”

“You’ll get pneumonia. Put them on!”

Like Joan, Lucy had total confidence in her own judgment of her nearest and dearest’s best interests. With slightly better grace than he might have mustered had he not been about to return to London, Strike took his trousers and put them on, balancing awkwardly and risking a fall onto the gravel path. By the time he’d added a shoe and sock to his real foot, Lucy had made him a fresh mug of tea along with her own.

“I couldn’t sleep, either,” she told him, handing over the mug as she sat down on the stone bench. It was the first time they’d been entirely alone all week. Lucy had been glued to Joan’s side, insisting on doing all the cooking and cleaning while Joan, who found it inconceivable that she should sit down while the house was full of guests, hovered and fussed. On the rare moments that Joan wasn’t present, one or more of Lucy’s sons had generally been there, in Jack’s case wanting to talk to Strike, the other two generally badgering Lucy for something.

“It’s awful, isn’t it?” said Lucy, staring out over the lawn and Ted’s carefully tended flower-beds.

“Yeah,” sighed Strike. “But fingers crossed. The chemo—”

“But it won’t cure her. It’ll just prolong—pro—”

Lucy shook her head and dabbed at her eyes with a crumpled piece of toilet roll she pulled out of her dressing-gown pocket.

“I’ve rung her twice a week for nigh on twenty years, Stick. This place is a second home for our boys. She’s the only mother I’ve ever known.”

Strike knew he oughtn’t to rise to the bait. Nevertheless, he said,

“Other than our actual mother, you mean.”

“Leda wasn’t my mother,” said Lucy coldly. Strike had never heard her say it in so many words, though it had often been implied. “I haven’t considered her my mother since I was fourteen years old. Younger, actually. Joan’s my mother.”

And when Strike made no response, she said,

“You chose Leda. I know you love Joan, but we have entirely different relationships with her.”

“Didn’t realize it was a competition,” Strike said, reaching for another cigarette.

“I’m only telling you how I feel!”

And telling me how I feel.

Several barbed comments about the infrequency of Strike’s visits had already dropped from his sister’s lips during their week of enforced proximity. He’d bitten back all irritable retorts. His primary aim was to leave the house without rowing with anyone.

“I always hated it when Leda came to take us away,” said Lucy now, “but you were glad to go.”

He noted the Joan-esque statement of fact, the lack of inquiry.

“I wasn’t always glad to go,” Strike contradicted her, thinking of the ferry, Dave Polworth and the smugglers’ caves, but Lucy seemed to feel that he was trying to rob her of something.

“I’m just saying, you lost your mother years ago. Now I’m—I might be—losing mine.”

She mopped her eyes again with the damp toilet roll.

Lower back throbbing, eyes stinging with tiredness, Strike stood smoking in silence. He knew that Lucy would have liked to excise Leda forever from her memory, and sometimes, remembering a few of the things Leda had put them through, he sympathized. This morning, though, the wraith of Leda seemed to drift on his cigarette smoke around him. He could hear her saying to Lucy, “Go on and have a good cry, darling, it always helps,” and “Give your old mum a fag, Cormy.” He couldn’t hate her.

“I can’t believe you went out with Dave Polworth last night,” said Lucy suddenly. “Your last night here!”

“Joan virtually shoved me out of the house,” said Strike, nettled. “She loves Dave. Anyway, I’ll be back in a couple of weeks.”

“Will you?” said Lucy, her eyelashes now beaded with tears. “Or will you be in the middle of some case and just forget?”

Strike blew smoke out into the constantly lightening air, which had that flat blue tinge that precedes sunrise. Far to the right, hazily visible over the rooftops of the houses on the slope that was Hillhead, the division between sky and water was becoming clearer on the horizon.

“No,” he said, “I won’t forget.”

“Because you’re good in a crisis,” said Lucy, “I don’t deny that, but it’s keeping a commitment going that you seem to have a problem with. Joan’ll need support for months and months, not just when—”

“I know that, Luce,” said Strike, his temper rising in spite of himself. “I understand illness and recuperation, believe it or—”

“Yeah, well,” said Lucy, “you were great when Jack was in hospital, but when everything’s fine you simply don’t bother.”

“I took Jack out two weeks ago, what’re you—?”

“You couldn’t even make the effort to come to Luke’s birthday party! He’d told all his friends you were going to be there—”

“Well, he shouldn’t have done, because I told you explicitly over the phone—”

“You said you’d try—”