Laing lay silent on the dirty floor, but Strike could almost feel the frantic workings of his filthy, desperate mind.

“I found Accutane in the house,” Strike told Shanker. “It’s a drug for acne, but it’s for psoriatic arthritis too. I should’ve known then. He kept it hidden in Kelsey’s room. Ray Williams didn’t have arthritis.

“I bet you had lots of little secrets together, didn’t you, Donnie, you and Kelsey? Winding her up about me, getting her exactly where you wanted her? Taking her for motorbike rides to lurk near my office… pretending to post letters for her… bringing her my fake notes…”

“You sick bastard,” said the disgusted Shanker. He leaned over Laing with his cigarette tip close to Laing’s face, clearly yearning to hurt him.

“You’re not burning him either, Shanker,” said Strike, pulling out his mobile. “You’d better get out of here, I’m going to call the cops.”

He rang 999 and gave the address. His story would be that he had followed Laing to the club and back to his flat, that there had been an argument and that Laing had attacked him. Nobody needed to know that Shanker had been involved, nor that Strike had picked Laing’s locks. Of course, the stoned neighbor might talk, but Strike thought it likely that the young man might prefer to stay well out of it rather than have his sobriety and drug history assessed in a court of law.

“Take all this and get rid of it,” Strike told Shanker, peeling off the fluorescent jacket and handing it to him. “And the gas canister through there.”

“Right y’are, Bunsen. Sure you’re gonna be all right with him?” Shanker added, eyes on Strike’s broken nose, his bleeding ear and hand.

“Yeah, ’course I will,” said Strike, vaguely touched.

He heard Shanker picking up the metal canister in the next room and, shortly afterwards, saw him passing the kitchen window on the balcony outside.

“SHANKER!”

His old friend was back in the kitchen so fast that Strike knew he must have sprinted; the heavy gas canister was raised, but Laing still lay handcuffed and quiescent on the floor, and Strike stood smoking beside the cooker.

“Fuckin’ ’ell, Bunsen, I fort ’e’d jumped you!”

“Shanker, could you get hold of a car and drive me somewhere tomorrow morning? I’ll give you—”

Strike looked down at his bare wrist. He had sold his watch yesterday for the cash that had paid for Shanker’s help tonight. What else did he have to flog?

“Listen, Shanker, you know I’m going to make money out of this one. Give me a few months and I’ll have clients queuing up.”

“’S’all right, Bunsen,” said Shanker, after brief consideration. “You can owe me.”

“Seriously?”

“Yeah,” said Shanker, turning to go. “Gimme a bell when you’re ready to leave. I’ll go get us a car.”

“Don’t nick one!” Strike called after him.

Mere seconds after Shanker had passed the window for the second time, Strike heard the distant sound of a police siren.