“Anyway, once I’d convinced him that I am who I am, that I’m not a journalist or a policewoman—”

“You told him the truth?”

“Yes, which was the best thing I could have done, because once he was convinced I was really me, he agreed to meet.”

“And what makes you think he’s genuinely going to meet you?” asked Strike.

“Because we’ve got leverage with him that the police haven’t.”

“Like what?”

“Like,” she said coldly, wishing that she could have returned a different answer, “you. Jason’s absolutely desperate to meet you.”

“Me?” said Strike, completely thrown. “Why?”

“Because he believes you cut your leg off yourself.”

“What?”

“Kelsey convinced him that you did it yourself. He wants to know how.”

“Jesus fucking Christ,” said Strike, “is he mentally ill? Of course he is,” he answered himself immediately. “Of course he’s mentally ill. He wants to cut his fucking leg off. Jesus fucking Christ.”

“Well, you know, there’s debate about whether BIID is a mental illness or some kind of brain abnormality,” said Robin. “When you scan the brain of someone suffering—”

“Whatever,” said Strike, waving the topic away. “What makes you think this nutter’s got anything useful—?”

“He met Kelsey,” said Robin impatiently, “who must have told him why she was so convinced you were one of them. He’s nineteen years old, he works in an Asda in Leeds, he’s got an aunt in London and he’s going to come down, stay with her and meet me. We’re trying to find a date. He needs to find out when he can get the time off.

“Look, he’s two removes from the person who convinced Kelsey you were a voluntary amputee,” she went on, both disappointed and annoyed by Strike’s lack of enthusiasm for the results of her solo work, but still holding out a faint hope that he would stop being so tetchy and critical, “and that person is almost certainly the killer!”

Strike drank more tea, allowing what she had told him to percolate slowly through his exhausted brain. Her reasoning was sound. Persuading Jason to meet her was a significant achievement. He ought to offer praise. Instead he sat in silence, drinking his tea.

“If you think I should call Wardle and pass this over to him—” said Robin, her resentment palpable.

“No,” said Strike, and the haste with which he answered gave Robin some small satisfaction. “Until we’ve heard what he’s… we won’t waste Wardle’s time. We’ll let him know once we’ve heard what this Jason’s got. When did you say he’s coming to London?”

“He’s trying to get time off; I don’t know yet.”

“One of us could go up to Leeds and meet him.”

“He wants to come down. He’s trying to keep all this away from anyone who knows him.”

“OK,” said Strike gruffly, rubbing his bloodshot eyes and trying to formulate a plan that would keep Robin simultaneously busy and out of harm’s way. “You keep the pressure on him, then, and start ringing round those numbers, see whether you can get a lead on Brockbank.”