The suspects, then – Margo still remained on the periphery, but he was fairly certain she didn’t have the skills or imagination to plan each death so carefully. Craig Derbyshire was a possibility. He had managed to hold down a job locally and put his past behind him, to a large extent. He had also displayed satisfaction at the mention of each death. His work alibi was likely to stand up to scrutiny, leaving him the weekends to plan and execute each murder – assuming his wife would cover for him. That seemed unlikely, if he was desperate to keep his time at the orphanage a secret from her. There was nothing more likely to attract her interest than to involve her in a deception. George Winter was homeless, a drug addict and beggar. He was the unfortunate victim of a life loaded against him before it had even begun. Did he have the wherewithal to plan and execute three murders to this level of detail? He was the only one without an alibi, but then again, he would have struggled to remember what year it was, never mind provide a detailed explanation of his movements during the past fortnight. Corstorphine wrote each name down on the wall as he considered them. That left William Booth, the butcher. He lived locally and worked for himself. Even so, with limited time, he could have got away and primed each death trap in readiness for the victim. He was also the only person with ready access to bone to make the devices. Finally, there was the gamekeeper, John Ackerman. The only link he had was with the laird and Oscar, but he had broken into the laird’s house. What about the other orphans? Those who had been on the council’s list, but they had so far been unable to track down?

Corstorphine shook his head, the job was looking impossible – chasing a murderer who left no forensic clues, only bizarre contraptions that must have taken hours to construct. He tried to get inside the murderer’s head, to imagine how they would have coped as a child, forgotten and unloved in that cold Victorian orphanage. How had any of them survived?

“Anything I can help with, sir?” Frankie’s enquiry brought him back to the present.

“Just trying to identify a likely culprit, Frankie. Someone clever enough to plan these murders without leaving any evidence connecting them to the scenes. Somehow, I don’t think it’s anyone we’ve put on the board.”

“Do you think there’s going to be another murder, sir? Is there someone we should be keeping an eye on?”