‘Ruth, how cold is it today? And you’re wearing flip-flops, no socks or tights, nothing. There you go: proof that a person can be inappropriately dressed and not stalking anyone!’ Charlie wasn’t angry, as she must have sounded, but a certain amount of force was necessary to stamp out irrationality. Was Ruth insane? Was Aidan Seed? If only the answer in both cases was ‘yes’, that would explain everything.

Apart from Mary Trelease’s behaviour. ‘Not me,’ she’d said, when Charlie had told her about Aidan’s claim that he’d killed her. Naturally, Charlie had asked her if she was implying Aidan had murdered someone else. Mary had denied it—‘I simply meant that I’m patently not dead’—but Charlie hadn’t felt good about it at all. The look on Mary’s face . . .

This man looks in a different way.

Charlie would have been lying if she’d told Ruth that a look in isolation could never be sufficient grounds for suspicion, though she doubted the man with the red bobble hat was anything to worry about.

‘I never wear socks,’ said Ruth. ‘My parents used to make me wear them every day, and a vest. They were obsessed with stopping heat escaping from their bodies. Our house was like a furnace, heating and gas fires on all year round.’ Her teeth started to chatter.

Charlie had to press the key-fob four times before her car’s lights flashed twice: unlocked. The battery was losing its power. She’d been meaning to buy a spare and put it in the glove compartment, but hadn’t got round to it. She opened the boot and handed Ruth her coat. ‘Maybe your man’s parents wouldn’t let him wear woolly hats, even in hailstorms,’ she said. Ruth didn’t smile.

Once they were in the car and driving, Charlie said, ‘Are you going to tell me why you had that piece about me from the paper in your coat pocket?’

‘You went through my pockets. I thought you would.’ Ruth seemed to shrink in her seat. ‘I’m sorry about . . . what happened to you. It must have been awful for you. You looked devastated in the photograph.’

‘We’re not going to talk about me,’ said Charlie firmly.

‘That’s why I waited for you on Friday. I was in such a state, I couldn’t have spoken to anyone else. After what you’d been through, I thought you’d be understanding.’