‘What do you mean?’ Simon pushed. ‘Do you mean the letters you’ve written to Sondra Halliday? The weird stories you’ve sent her? You must have known she’d pass them on to us.’

‘You can trust us, Isobel. Really.’

Christ, could Sam not rein himself in? Handling suspects sensitively was one thing, but there was only so much of his soft-consonant smarming that Simon could take. Gibbs was right; he’d been letting off steam about it in the Brown Cow recently, after he and Sam had interviewed two armed robbers who’d shot and killed three women at the Combingham branch of Santander. ‘His voice was one step away from being a fucking spa treatment,’ he’d said about Sam.

Isobel Sturridge had stopped talking and was tear-biting again.

‘Has your brother helped you to commit these murders?’ Simon asked. Liam Sturridge’s alibis had been proved solid, but that didn’t mean he hadn’t arranged it all and delegated the dirty work to his sister.

Isobel looked disorientated for a second or two, then shocked, as if something outrageous had been suggested. ‘Liam has nothing to do with any of this,’ she said in a clear, matter-of-fact voice.

‘Whereas you do – correct?’ Fuck. Simon had pounced on that too quickly. Isobel drew her head back, as if afraid he might spit at her.

‘We know you’re Elise Rudolphy’s daughter,’ he told her. ‘An American poet, name beginning with E. Like the three poets whose words you’ve used in the little white books you give to your victims. Why do you do that, Isobel?’

No answer.

‘Why did you give Kim Tribbeck a book first and then not kill her? All your other victims, you’ve planted the white book, unseen, and then killed them very soon after. Why’s Kim different? Is it because you didn’t manage to slip the book into her bag – you were interrupted? Or because she was your brother’s girlfriend for a while?’ Simon’s adrenaline morphed into anger without warning. ‘Crying’s not an answer! Tell me!’

‘Simon,’ Sam murmured.

‘All right then, don’t tell me. Tell him. Look at him! Look at that face: ready to lap up any bullshit you cough up. Why not take advantage? Did you know Linzi Birrell and Rhian Douglas personally? You worked at Rudolphy’s until it closed. Was Linzi a customer? She lived locally, so she easily could have been. Was Josh Norbury a customer? Rhian Douglas and Angela McCabe didn’t live in the Culver Valley – how did you persuade them to let you into their homes?’

‘Browbeating her’s not going to achieve anything,’ said Sam quietly.

‘Yeah, well, not everything has to be an achievement.’