I’ve never been good at thinking things through. My brain can’t always work its way round a maze of information, like some people’s do with such ease, as if they were floating above it. But I try now. Were they lovers? There’s a hint of that, but nothing specific. Maybe he didn’t trust her. I don’t, and I don’t know her as well as he appears to. The letter doesn’t prove that she came after Nick, meaning to disrupt his life, but it’s surely enough to make the police accept that Anna may well be the key to all this.

What else does it tell me?

Anna made that first move towards reconciliation by getting in touch with a close family friend the year before she moved into this area. She didn’t take Angus’s advice and speak to her family, but she did make contact with Nick. She denies being in touch with Alex, but she could have lied. I can imagine a scenario where Alex got in touch with her as part of his recovery, and she spotted an opportunity and persuaded him to put pressure on Nick, having already started the process the evening before.

Why did Anna go to see Angus in the first place? Because she was lonely? I remember my own first impression of Nick’s boss: utterly in control, courteous and charming. I’d guess she contacted him and not his wife because she’s more comfortable with men than she is with women. And the Moodys rather than the Ritchies because of what Tim did to her. He had betrayed her parents’ friendship and made a mockery of her childhood.

As for the women, if Cora and Jess Wells were anything like Cassie and me, they would have been in and out of each other’s houses when the children were tiny. I sigh inwardly. Is any of this even relevant? I should call the police.

This house is so cold. I pull a soft woollen throw from the back of the armchair and wrap it round my shoulders, then go to the door, open it and wander out into the street. I breathe in the heady scent of the wisteria that covers the house next door, its flowers dripping shades of purple. It’s such a tranquil road, but who knows what goes on behind the prettily painted walls?