‘A white man who is trying to right some perceived wrong,’ Dr Stephen said. ‘A man who is punishing his victims. These are all planned attacks. Very carefully planned attacks. These are not confrontational homicides, these are revenge homicides. The unsub is trying to right a wrong by the only means at his disposal – extreme violence. He is the product of a place where violence is the means of achieving your aims.’

The resentment was coming off Gane like steam, but to me Dr Stephen was making sense. I thought of the terrible neatness of those carotid thrusts and the ease with which they opened arteries that could never be closed again. It was the work of a man who was remaking the world.

‘Maybe he’s just a nutter,’ Gane said.

Dr Stephen smiled at him with a kind of embarrassed pity. ‘Then he is a nutter – your term, detective, not mine – who is restoring control over what he perceives to be a mad world. Honour. Power. Control. That’s what matters to him. And when you find him, as you no doubt will, you will find a man who needs to control other men, a man who needs that more than anything in the world.’

‘So you don’t really know anything about him at all?’ Gane persisted.

‘Look, the reason I’m in this room is because these are stranger killings,’ Dr Stephen said. ‘Most of the homicides you attend, the killer and the victim are known to each other. The husband who murders his wife because of her infidelity, the mother who murders her child, the drug dealer who murders his business associate.’ He paused. ‘That link does not exist with a serial killer. He is not known to the victim. He is not a husband, a business associate, a friend. But the unknown sub leaves evidence. Psychiatric evidence. Behavioural evidence. Ritualistic evidence. The remnants of fantasy and madness.’

On the other side of the glass walls I saw Scarlet Bush being escorted to the conference room.

‘Ah, this is Ms Bush,’ Swire said when she entered the room, ‘who some of you will know already as crime correspondent for the Daily Post.’

The reporter circled the table, shaking hands and making smiling eye contact with everyone, including me. She played it as if we had never met. Then she took her place at the top of the conference table, next to Dr Stephen.

‘This is the plan,’ Swire said.

The shock of these words jolted Mallory upright and made the pain at the base of my spine pulse with alarm. Whitestone and Gane exchanged a startled look.

What plan?