He crosses the woodworm-riddled threshold, entering a hallway patterned with red and black tiles. The plaster on the walls hangs loose, the flocked wallpaper holding it together as best it can. In places it bulges with fallen brickwork while in others it’s dark and flaky, charred by fire. A wooden staircase leads up to the next floor, its banisters twisted and blackened. To his right, the floor has given way so that getting into the living room now takes a small leap of faith. Beyond the hole, a team of white-clad scene-of-crime officers are combing through the building’s past. He steps across to join them.

The house has clearly been empty for years, but someone has been here more recently than that. Village kids poking round, smoking dope perhaps. He sees the remains of a small fire on the floor; around it a few dozen cigarette butts and spent matches. Much of the room is smoke blackened, and parts of it are water damaged. Curiously, some parts are almost pristine: a standard lamp, dusty, its red shade unfaded; the curtains hanging across the patio doors at the far end could be brushed off and made good. It’s as though the fire has moved through the room, picking and choosing its targets with care.

Again he has that sensation of being watched, and he searches the room, half-expecting the country bumpkin gardener to appear from behind the sofa. Then he sees the portrait above the mantelpiece, a small framed oil painting of the head and shoulders of a man. The man is wrapped in a dark coat pulled tight to the neck, around which is tucked a loose red scarf. His face is incongruously large. The gray skin hanging in loose folds round his cheeks and jowls makes him look both fat and malnourished at the same time. Here and there are brushstrokes of oranges and reds that might be the distant reflection of light on the horizon. The eyes of the man in the picture are wide and bright and mad. It is these eyes that follow him as he moves through the room. There’s a signature in the bottom right-hand corner, hard to make out, and a plaque built into the base of the frame that gives him the painting’s title: The Fire Watcher.

The frame is much smaller than the rectangle of paler wall that surrounds it, indicating that another picture once hung here, something that must have been moved after the fire. Something wider than it was tall . . . landscape, rather than portrait. He scans the room and finds the likely candidate propped against a nearby armchair, a dull watercolor of the Peak District. He pulls out his mobile and snaps a photo of it.

One of the SOCOs glances up at him.

“Has anyone moved this?” he asks.

The man stares at him blankly.

“You need to dust it for prints. The one on the wall, too.”