Pirie had moved next door to the viewing room. McNab was already conscious of being watched. That sensation was the only psychic phenomenon he accepted, mainly because it had saved his life on a couple of occasions. Once upon a time, Pirie had tried to explain the psychological reasons for thinking that someone was watching you. McNab had started listening but had soon grown weary. All those words for something he simply knew to be true.

The other thing McNab knew, from instinct or intuition, was when he was in the presence of evil.

He glanced up as the door opened and Janice stood aside to let McLaughlin enter. In that moment, McNab felt the hairs on his arms rise in warning. Evil, it seemed, had many forms. In this case, it had taken on the role of Santa Claus via a red jacket, fastened over a large belly, fluffy white hair with beard to match, and rosy cheeks.

McNab found himself wanting to say ‘Ho, ho, ho’.

McLaughlin immediately came forward, hand outstretched. ‘It’s a pleasure to meet you, Detective Inspector . . . oh sorry, Detective Sergeant McNab. I’ve been following your career quite closely during my studies.’

McNab did not accept the handshake, which he knew was a wrong move since it then put McLaughlin at an advantage. Although his head had told him to shake hands, his arm, with the hairs still standing, had simply refused.

McNab glanced at Janice to check how she was faring but couldn’t read her expression or body language. As for McLaughlin, he gave an avuncular laugh and sat down.

McNab began the formalities but McLaughlin interrupted him to ask in a puzzled fashion where Professor Pirie was. ‘I understood he would be present.’

‘That wasn’t possible,’ Janice said coolly. ‘Professor Pirie has classes all morning.’

McLaughlin raised a quizzical eyebrow. ‘Not according to his online timetable.’

McNab could almost see Pirie shaking his head in the next room at the way things were going. Perhaps even memorizing the scene for the subject of future lectures.

‘How Not to Start an Interview with a Psychopath’ seemed an appropriate title.

Eventually they were ready.

McLaughlin, McNab thought, looked keen. Unsurprising really, the way things had transpired up to now. He sat relaxed in the chair, a small, contented smile on his pink lips.

Trying to ignore the self-satisfied air emanating from McLaughlin, McNab said, ‘The purpose here is for you to tell us everything you remember.’

A cognitive interview normally began with a free recall. Something McLaughlin would know. From the look on his face he had his story all ready and waiting.

‘No bother,’ McLaughlin replied.

‘So, Mr McLaughlin,’ Janice said, ‘where were you exactly when you first heard that Mary McIntyre was missing?’

McLaughlin’s reaction to this was a joy to behold. Whatever he’d thought they might start with, it certainly wasn’t that question. He looked nonplussed, but only for a moment.

‘My exact location?’ he said slowly.

McNab could almost see the wheels turning as McLaughlin restructured his no doubt well-rehearsed story.