“I’ll be vigilant. I’ve got two rape alarms.”

Strike did not look reassured.

They disembarked at New Scotland Yard and were shown upstairs at once, into an open-plan office where Wardle stood in his shirtsleeves, talking to a group of subordinates. When he saw Strike and Robin he left his colleagues at once and led the detective and his partner into a small meeting room.

“Vanessa!” he called through the door as Strike and Robin took seats at an oval table, “have you got the letters?”

Detective Sergeant Ekwensi appeared shortly afterwards with two typewritten sheets protected in plastic slips and a copy of what Strike recognized as one of the handwritten letters that he had given Wardle in the Old Blue Last. Detective Sergeant Ekwensi, who greeted Robin with a smile that the latter again found disproportionately reassuring, sat down beside Wardle with a notebook.

“You want coffee or anything?” Wardle asked. Strike and Robin shook their heads. Wardle slid the letters across the table to Strike. He read both before pushing them sideways to Robin.

“I didn’t write either of them,” Strike told Wardle.

“I didn’t think so,” said Wardle. “You didn’t answer on Strike’s behalf, Miss Ellacott?”

Robin shook her head.

The first letter admitted that Strike had indeed arranged the removal of his own leg because he wished to be rid of it, confessing that the story of an Afghan IED was an elaborate cover-up, and that he did not know how Kelsey had found this out, but implored her not to tell anybody else. The fake Strike then agreed to help her with her own “encumbrance” and asked where and when they could meet face to face.

The second letter was brief, confirming that Strike would come and visit her on the third of April at 7 p.m.

Both of the letters were signed Cameron Strike in thick black ink.

“That,” said Strike, who had pulled the second letter back towards him after Robin had finished reading it, “reads as though she wrote back to me suggesting a time and place.”

“That was going to be my next question,” said Wardle. “Did you get a second letter?”

Strike looked towards Robin, who shook her head.

“OK,” said Wardle, “for the record: when did the original letter from—” He checked the photocopy. “Kelsey, she’s signed herself—come in?”

Robin answered.

“I’ve got the envelope back in the nut—” The ghost of a smile passed over Strike’s face. “—in the drawer where we keep unsolicited letters. We can check the postcode, but as far as I can remember it was early this year. Maybe February.”

“OK, excellent,” said Wardle, “we’ll be sending someone over to retrieve that envelope.” He smiled at Robin, who was looking anxious. “Calm down: I believe you. Some total nutter’s trying to frame Strike. None of it hangs together. Why would he stab a woman, dismember her and then mail her leg to his own office? Why would he leave letters from himself in the flat?”