Jonah left her there. He climbed the stairs and entered Louise and Niall’s bedroom. McCullough and her assistant had stripped the sheets back from the bed, exposing a tide mark of brownish red. Hanson was standing to one side, a satisfied expression on her face.

Despite having been prepared for this, Jonah found himself a little nauseated at the extent of the blood. It had soaked through most of the mattress. The only white details remaining were the little plastic buttons dented into its top.

‘I’m confident we’ll be able to get DNA,’ McCullough said. ‘The underneath hasn’t entirely dried yet.’

‘Good,’ Jonah said. ‘And quantity … You’d say it looks enough for him to have died here?’

‘I’ll get you a volumetric estimate,’ McCullough said, ‘but on a visual reckoning it looks more than enough.’

Jonah gave her a small smile. McCullough was renowned for being difficult to pin down. She hated committing herself to theories, and tended to offer stark fact with no interpretation. For her to give him that much meant she had no doubt at all.

Hanson went back downstairs with him. He let her walk into the music room first. Louise’s expression looked hopeless. Her fear was stark and obvious even viewed through the strings of her harp.

‘Louise Reakes, I’m arresting you for the murder of Alex Plaskitt, and for perverting the course of justice,’ Hanson began.

‘I’m sorry for lying,’ Louise said, before she could go on. ‘I’m really sorry.’

‘Did she say anything else?’ Lightman asked an hour later. His eyes were on the pale, sick-looking face of Louise Reakes.

He, Jonah and Hanson had gathered briefly in the observation room. Louise’s solicitor was on his way over. Jonah had gone into the interview room to tell her, but Louise had said nothing. Done nothing. He wondered whether she had really understood him.

‘Not a word,’ Hanson murmured. ‘We both tried asking her why she’d lied, but we only got head shakes.’

‘Any news on the husband?’ Jonah asked.

‘No reply from his mobile,’ Lightman told him. ‘Presumably in flight.’

Jonah nodded. He didn’t go on to say anything more yet. About the significance of the blood being in Louise and Niall Reakes’s marital bed. About the fact that Alex Plaskitt had been married to a man and yet had almost certainly died in bed with a woman. There were too many questions that needed answering, and no way of making sense of any of it without making a lot of strange assumptions.

‘Juliette, I want you and Domnall to go and see April Dumont. And we should talk to Alex’s husband again as soon as we can. It’s high time we found out whether Alex and Louise actually knew each other before that night, and I doubt Louise will tell us.’