“Then, of course, he killed Lorna. He had to leave the scaffolding on the kitchen roof because he was running out of time to keep up the alibi he’d set himself. Of course, once the murder was common knowledge, Sarah must have realized her father was implicated. The girl must have been under colossal strain all last week. I suppose your arrest made things even worse for her, Paddy. Then when she heard about our experiments with the scaffolding, she must have felt sure the net was closing around her father.

“She must have realized that the lie she’d told the police about you in the music room would be found out. Incidentally, I don’t think she lied out of particular malice—at that stage, after all, it wasn’t clear that the police were going to arrest you. I think she was just trying to cloud the issue in every conceivable way possible. I think what drove her to commit suicide was a combination of factors. She knew her father was a killer and she couldn’t bear it, but she still wanted to protect him, and the only way she could do that was to kill herself. Just confessing wouldn’t have been enough. She’d never have been able to make up a story that would have satisfied the police. And she probably felt that if she gave herself up to the police, the very thing that she was trying to avoid would happen—her father would give himself up to protect her.

“As it was, I’m not altogether sure he would have done. He was happy enough for her to carry the blame after her death. That’s what I find most inhuman about him.” She paused to pour out more coffee. “God, my throat is sore. I’m amazed there are hardly any bruises on it. I thought he was going to kill me.”

Paddy looked puzzled. “But everyone seemed to be satisfied after Sarah’s death that the whole thing had been cleared up. What made you think you knew better?”

“Apart from a general sense of superiority, she means,” said Cordelia with a rather grim smile.

“I finally got on the right track when I asked Jessica Bennett a question we should have asked her when we first interviewed her. When I saw her yesterday, I wanted to ask her if she’d seen Sarah at all on that Saturday evening—just for my own satisfaction, I suppose, though I did have one or two doubts about Sarah’s confession. It seemed so superficial, so lacking in feeling and detail. But Jessica’s answer put Sarah out of the running. She said she’d seen Sarah going out of Longnor at about quarter past seven.