Gregory cut himself off.

“—distracted, you know.”

“So, even once your father had recovered, he still thought Creed had taken Margot?”

“Oh yeah, definitely,” said Gregory, looking mildly surprised that this was in question. “They ruled out all the other possibilities, didn’t they? The ex-boyfriend, that dodgy patient who had a thing for her, they all came up clean.”

Rather than answering this with his honest view, which was that Talbot’s unfortunate illness had allowed valuable months to pass in which all suspects, Creed included, had had time to hide a body, cover up evidence, refine their alibis, or all three, Strike took from an inside pocket the piece of paper on which Talbot had written his Pitman message, and held it out to Gregory.

“Wanted to ask you about something. I think that’s your father’s handwriting?”

“Where did you get this?” asked Gregory, taking the paper cautiously.

“From the police file. It says: ‘And that is the last of them, the twelfth, and the circle will be closed upon finding the tenth’—and then there’s an unknown word—‘Baphomet. Transcribe in the true book,’” said Strike, “and I was wondering whether that meant anything to you?”

At that moment, there came a particularly loud crash from overhead. With a hasty “excuse me,” Gregory laid the paper on top of the tea tray and hurried from the room. Strike heard him climbing the stairs, and then a telling-off. It appeared that one of the twins had overturned a chest of drawers. Soprano voices united in exculpation and counter-accusation.

Through the net curtains, Strike now saw an old Volvo pulling up outside the house. A plump middle-aged brunette in a navy raincoat got out, followed by two boys, whom he guessed to be around fourteen or fifteen. The woman went to the boot of the car and took out two sports bags and several bags of shopping from Aldi. The boys, who’d begun to slouch toward the house, had to be called back to assist her.

Gregory arrived back at the sitting-room door just as his wife entered the hall. One of the teenage boys shoved his way past Gregory to survey the stranger with the amazement appropriate to spotting an escaped zoo animal.

“Hi,” said Strike.

The boy turned in astonishment to Gregory.

“Who’s he?” he asked, pointing.

The second boy appeared beside the first, eyeing Strike with precisely the same mixture of wonder and suspicion.

“This is Mr. Strike,” said Gregory.

His wife now appeared between the boys, placed a hand on their shoulders and steered them bodily away, smiling at Strike as she did so.

Gregory closed the door behind him and returned to his armchair. He appeared to have momentarily forgotten what he and Strike had been talking about before he had gone upstairs, but then his eye fell upon the piece of paper scrawled all over with his father’s handwriting, dotted with pentagrams and with the cryptic lines in Pitman shorthand.

“D’you know why Dad knew Pitman shorthand?” he said, with forced cheerfulness. “My mother was learning it at secretarial college, so he learned it as well, so he could test her. He was a good husband—and a good dad, too,” he added, a little defiantly.

“Sounds it,” said Strike.

There was another pause.

“Look,” said Gregory, “they kept the—the specifics of Dad’s illness out of the press at the time. He was a good copper and it wasn’t his fault he got ill. My mother’s still alive. She’d be devastated if it all got out now.”

“I can appreciate—”

“Actually, I’m not sure you can,” said Gregory, flushing slightly. He seemed a polite and mild man, and it was clear that this assertive statement cost him some effort. “The families of some of Creed’s victims, afterward—there was a lot of ill feeling toward Dad. They blamed him for not getting Creed, for screwing it all up. People wrote to the house, telling him he was a disgrace. Mum and Dad ended up moving… From what you said on the phone, I thought you were interested in Dad’s theories, not in—not in stuff like that,” he said, gesturing at the pentagram-strewn paper.

“I’m very interested in your father’s theories,” said Strike. Deciding that a little duplicity was called for, or at least a little reframing of the facts, the detective added, “Most of what your father wrote in the case file is entirely sound. He was asking all the right questions and he’d noticed—”

“The speeding van,” said Gregory quickly.

“Exactly,” said Strike.

“Rainy night, exactly like when Vera Kenny and Gail Wrightman were abducted.”

“Right,” said Strike, nodding.

“The two women who were struggling together,” said Gregory. “That last patient, the woman who looked like a man. I mean, you’ve got to admit, you add all that together—”

“This is what I’m talking about,” said Strike. “He might’ve been ill, but he still knew a clue when he saw one. All I want to know is whether the shorthand means anything I should know about.”

Some of Gregory’s excitement faded from his face.

“No,” he said, “it doesn’t. That’s just his illness talking.”

“You know,” said Strike slowly, “your father wasn’t the only one who saw Creed as satanic. The title of the best biography of him—”

“The Demon of Paradise Park.”

“Exactly. Creed and Baphomet have a lot in common,” said Strike.

In the pause that followed, they heard the twins running downstairs and loudly asking their foster mother whether she’d bought chocolate mousse.

“Look—I’d love you to prove it was Creed,” said Gregory at last. “Prove Dad was right all along. There’d be no shame in Creed being too clever for him. He was too clever for Lawson, as well; he’s been too clever for everyone. I know there wasn’t any sign of Margot Bamborough in Creed’s basement, but he never revealed where he’d put Andrea Hooton’s clothes and jewelry, either. He was varying the way he disposed of bodies at the end. He was unlucky with Hooton, chucking her off the cliffs; unlucky the body was found so quickly.”

“All true,” said Strike.

Strike drank his tea while Gregory absentmindedly chewed off a hangnail. A full minute passed before Strike decided that further pressure was required.

“This business about transcribing in the true book—”

He knew by Gregory’s slight start that he’d hit the bullseye.

“—I wondered whether your father kept separate records from the official file—and if so,” said Strike, when Gregory didn’t answer, “whether they’re still in existence.”

Gregory’s wandering gaze fixed itself once more on Strike.

“Yeah, all right,” he said, “Dad thought he was looking for something supernatural. We didn’t know that until near the end, until we realized how ill he was. He was sprinkling salt outside our bedroom doors every night, to keep out Baphomet. He’d made himself what Mum thought was a home office in the spare room, but he was keeping the door locked.

“The night he was sectioned,” said Gregory, looking miserable, “he came running out of it, ah, shouting. He woke us all up. My brother and I came out onto the landing. Dad had left the door to the spare room open, and we saw pentagrams all over the walls and lit candles. He’d taken up the carpet and made a magic circle on the floor to perform some kind of ritual, and he claimed… well, he thought he’d conjured some kind of demonic creature…