Charlie smiled. “So are you. That’s why she makes you feel uneasy. You prefer people who are nothing like you—and you trust them more.”

“Even if Hannah did it, that doesn’t answer the main question,” said Simon. “Why do it in such an elaborate, counterintuitive way? Everyone knows knives are for stabbing, not for suffocating.”

“Shh,” said Charlie, paranoid that the other lunchers in the café had abandoned their own conversations in order to listen to a more interesting one. “I don’t know. I can’t see the logic behind it.”

“Unless?” Simon prompted.

“Unless it was symbolic. Making some kind of point.” Charlie cut another small piece off her spinach and goat cheese tart. She was too full to eat any more, but it was there. What she really wanted to do was squash it with the back of her fork and make green and white gunge ooze through the tines. She reminded herself that she was a grown-up and resisted the urge.

“So your scrote didn’t want to stab Damon Blundy, but he did want to kill him with a knife,” she said. “He also wanted to write big red words on the wall—and because he didn’t stab Blundy, he couldn’t use his blood. He had to inconvenience himself by bringing paint and a brush. The whole murder scene’s screaming, ‘I could so easily have stabbed him, I prepared for a stabbing, a stabbing would have created all the conditions I wanted, but I didn’t stab. I killed him with a knife, but not in the obvious way.’ Ow!” Charlie yelped as Simon grabbed her hand with both of his.

“That’s it,” he said, his eyes shining as if someone had turned up a brightness dial inside his head. “He didn’t stab, but Blundy’s no less dead than if he had.”

“Yes, but it’s more than that,” said Charlie, wanting to make sure Simon hadn’t missed what she thought was her best point. “It’s not only ‘I didn’t stab him, but he’s no less dead than if I had.’ It’s ‘I didn’t use the knife in the way knives are meant to be used, but the end result is the same.’ It’s about knife use specifically—a knife not being used in the way that it normally is. I’d say the killer wants you to focus on two questions: why was he so keen to use a knife to kill Blundy, and why was he determined to use it so . . . unconventionally?”

Simon’s phone had started to vibrate on the table, but he was busy mouthing something to himself silently and didn’t notice. Charlie picked it up with her free hand. “Hello?”

“Oh.” A surprised-sounding woman’s voice. “I was hoping to speak to DC Simon Waterhouse.”

“I’ll pass you over. Who’s calling?”

“Gemma Dobson. I’m Paula Riddiough’s PA.”