When he had finished, he’d pulled out what looked to Trefor like a lens cap. Fletch had grinned. “It’s an external infrared filter.”

“What does that mean in plain English?”

“It means I can see things invisible to the human eye.”

“Aye. We’d learn a lot about folk if we all had one of those.”

Fletcher had begun to take pictures in Trefor’s workroom. The dolls on their shelves. The paint pots, the real hair and eyes.

He had wandered off down the corridor, toward the front of the shop. Trefor hadn’t paid him much heed. Fletcher was a friendly enough chap, but nervy and twitchy, as if his body was charged with electricity. He’d let him get on with it.

After a while, Trefor had washed his paintbrushes, wiped over his workbench. The usual end-of-the-day routines.

He was just about to turn out the light when Fletch came barreling in.

“You have to see this,” he’d said, jerking his head in the direction he’d just come. “This is seriously weird.”

Trefor had lumbered after him with low expectations.

A dim light was on. Fancy dress costumes lay in haphazard piles. One clothing rack was pressed against the wall. When he’d agreed to rent the place all those years ago, Cooper Clifton had offered to redecorate. The smell of fresh paint had stayed with Trefor for days.

“Look,” Fletch had said, pointing toward the far wall. “Can you see it?”

Trefor had looked at him as if he was mad.

“It’s a wall.”

“Yes,” said Fletch, fumbling with his camera. “Now, look at this.”

At first, Trefor could see only the magenta hue of the infrared images on the digital screen. Specks of dirt and lint and smudges that weren’t apparent to the naked eye. But as he became accustomed to the peculiarities of the picture, he saw what Fletch was talking about.

Spatter.

He blinked several times. The spots were clustered together, as if something had sprayed against the wall. Beneath it were smears, but they were patchy, like negatives, as if someone had tried with limited success to wipe them clean.

Fletcher was explaining the science behind his discovery, how infrared has longer wavelengths than visible light. But Trefor was not interested. The facts were simple. The camera had cut through multiple layers of paint to reveal this secret.

“What do you think it is?” said Trefor. But he had known.

During the early years, when he’d been young and hungry for action, when he had left the Royal Marines and taken a job abroad in security for an oil company, before he had realized the cost of killing, he had stabbed a thief. The blood had sprayed the wall in exactly the same way.

Someone had died here.