Harper looks uncomfortable. ‘Just supporting the community,’ she says. ‘I mean, since we’re going to be part of it and everything.’

‘I do hope you’ll bid for something in the auction,’ I say sweetly. ‘We’ve been so lucky with our donors. Last year, someone paid ten thousand pounds for a reserved parking space outside Asher Brook Primary.’

‘I’m surprised it didn’t go for more,’ Tom says. ‘A parking spot near that school is rarer than hen’s teeth.’

‘Oh, your son goes to Asher Brook?’ Harper says, with a creditable attempt at surprise. ‘We’re hoping to get our boys in there.’

‘Then you must let me introduce you to Mark Bristow,’ Tom says kindly. ‘He’s in charge of admissions there. Good friend of mine.’

I can almost hear Harper’s knicker elastic snap.

Her husband, Kyle, hasn’t yet said a word. He looks as awkward in his black tie as Tom looks at ease in his.

A colleague of mine intercepts us as we merge into the throng heading towards the ballroom. An informal consult on a complex case: I lose track of Tom and the Conways, and don’t pick them up again until we are all about to sit down.

Stacey’s table is next to ours, of course. Our gilt chairs are back to back, and as I sit down, she taps me on the shoulder.

‘That’s Felix,’ she says, indicating the man two seats away from her.

Not what I expected. Much older, for a start: at least twenty years older than Stacey. Better looking than the few photographs Tom managed to find online: sharper jaw, sharper eyes. Clean-shaven, thick brown hair. His expression is flinty.

He nods curtly at me when he sees his wife pointing, and carries on talking to his neighbour, a middle-aged woman I vaguely recognise from a gardening show that was cancelled a few years ago. She looks as if she’s been kidnapped by a murderer and dressed in his mother’s clothes.

Harper waves enthusiastically from her table on the far side of ours. Clearly her presence at the gala is not a coincidence. She’s done her research: she’s found out where I work, the causes I support, the school my son attends. I assume it’s for much the same reasons I’ve gone to so much effort to make a friend of Stacey: until we exchange contracts, none of us have a done deal.

At least I hope that’s the reason.

SETtalks | psychologies series

Science ♦ Entertainment ♦ Technology

Inside the mind of a psychopath | Original Air Date 9 July

The transcript below has been lightly edited for length and clarity.

Who remembers the name Susan Atkins?

Well, I don’t blame you for not recognising it: it’s a common enough name. What about Patricia Krenwinkel?

Ah. We’re getting closer now. Show of hands … a few of you.

Charles Manson?