Then a young couple appeared on the opposite bank and began to walk slowly across the bridge. Kotsev moved back from the parapet when he heard the footsteps. He brushed against her as he turned, and Fry caught a whiff of his scent when he touched her. She inhaled instinctively, trying to read some elusive meaning in a smell.

‘Kalina Tet-a-tet,’ he said quietly. ‘It’s Russian.’

Fry met his gaze for a moment, wondering how he’d known what she was thinking.

Cooper retrieved his beer and switched on the TV. But the film had already started, and it didn’t look quite so interesting after all. In fact, he thought he’d probably seen it before, and just forgotten the title. So he disentangled himself from the cat and picked up his phone again. He dialled a number from his phone book.

‘Hi, it’s me. What are you doing?’

And immediately it was as if he’d been sucked into some kind of time slip. Time went by without him being aware of it, because he was in a world when time didn’t really exist. When he next looked at his watch, the call seemed to have lasted for nearly an hour. He’d finished his beer, walked into the kitchen, opened the fridge, and come back with another bottle, all without breaking concentration. It was a miracle the way the mind could focus on the important things.

‘Better go. Are you on duty tomorrow . . . ? I’ll see you, then.’

Finishing the call, he decided to go to bed early. But he lay awake for a while with the cat lying on his duvet, purring like a mobile generator. He always thought a feline in the bedroom was appropriate, in a way. A cat was the Celtic equivalent to the dog Cerberus – the guardian at the entrance to the Underworld. Randy could watch over him as he slipped across the vulnerable threshold between waking and sleep.

Tonight, his brain was already wandering out of his control, following its own path. He was remembering random incidents from his past when reality might have been different from what he’d perceived. There had been moments, of course. There’d been times when he thought he saw things that didn’t exist, when he’d woken to a voice in the night and realized it was only a dream. There had been entire periods of his life when everything had been dark and twisted, and out of proportion. As a teenager, his whole world had seemed out of kilter. But you could only recognize that later, couldn’t you? Reality was a matter of perspective.