The front door of the building is locked, but he knows there’s a side entrance down the alley to the left. The small door has been boarded over, but the wooden planks are loose and he pushes them aside easily. The door behind swings open with a loud creak, and the stench of damp and urine is almost overpowering. He considers calling it in, but what is it exactly? A shadow glimpsed in the night? No one’s going to come rushing out for that, and certainly not on his say-so. The thought reminds him of his mobile and he pulls it out, uses the light on the camera to negotiate his way through the rubble. The corridor he’s in leads directly to a set of stairs, no other doors. An emergency exit. He takes the stairs slowly, broken glass from the smashed lighting above crunching beneath his feet. Another door, its emergency bar long broken, stands open and leads into a wide room scattered with abandoned office furniture. There’s a bit more light here, street light filtered by the cracked and missing windows.

The room is enormous and stretches the entire length of the building, but his view is obstructed by a number of pillars that support the roof. There are desks and chairs as well, partitioning that once would have separated the cubicles of bored call-center workers. Plenty of hiding places. Dark corners that neither the diffuse orange street light nor his tiny pinprick torch can reach. He moves forward slowly, edging his way nearer to the windows on the front of the building, his eyes searching the darkness for some telltale movement, a shadow that seems out of place. He glances out quickly through one of the broken windows at the street below, but there’s no sign of anyone. The battery on his mobile beeps again. He reaches the part of the building that lies directly opposite his own flat. There’s the cracked glass pane that looks like a black flame, only from this side the flame is orange and bright. Through it he can see his own living room, the cheap eBay sofa, the IKEA breakfast bar, the bookcases.

Then the window shatters, bursts into a thousand razor-sharp quills.

Tyler reacts instinctively, dropping his mobile and raising his arms to protect his face. He takes a step backward, crouching down, the sound of the shattered glass settling around him. His heart smashes against his rib cage. He looks down at the stone as it comes to a standstill. He hears laughter and looks outside to see a bunch of kids haring away up the road. He exhales loudly. They must have heard him coming and found another way out of the building.