Steganography was the art of concealing a message within another message. The Service’s technical department had come across a lot of men hiding images of child abuse in apparently innocent jpegs. It was an obvious enough idea to use similar technology for our own purposes.

I downloaded the file, ran it through decrypting software, braced myself for whatever revelation demanded such concealment.

Filename: Catalyst.avi

From the opening frame it looked like CCTV or a spycam: black and white, wide-angle lens, high on a wall. The room was plush: white furniture, glass coffee table. I thought maybe a hotel room, but the décor wasn’t coordinated enough. Not one I recognised. A suited man stood alone at the window, turned so that his face was obscured.

From the angle I’d guess the camera was concealed in a thermostat or vent. It looked down on the top of a chest of drawers by the far wall and a sofa directly below. There was a window through which you could see an area of roof then what may have been an adjacent wing of the same building.

I cast an eye around the café again, then clicked play.

No audio. There was a briefcase on the glass coffee table, a decanter, a heavy-looking square ashtray. There was a framed picture on the wall: a horse and rider travelling through a mountainous landscape.

He browsed a bookcase at the back, checked his watch. I still couldn’t see his face.

Watching people who think they are alone had never lost its attraction. The first few times I expected some secrets to be revealed, but now it was the very absence of secrets that appealed. The fact that humans were all the same, the thrill of their mundanity, our shared solitude.

At fifty seconds he turned, poured a drink, and you saw his face for the first time.

I hit pause. Then I studied the room that he occupied again, then I enlarged the image to see the face more clearly.

It was me.

I was clean-shaven, smart, in a suit similar to ones I owned but not exact. I stood in a room I’d never been in. It was my face, my physicality. I hit play, watched myself sit on the sofa, pick up cigarettes, change my mind and put them down. At one minute forty-five seconds another man entered.

He looked Central Asian, dark hair swept in a heavy fringe, holding an old-school Nokia 130.

I didn’t recognise him. The man said something, locked the case but left it lying on the coffee table. I appeared to offer him a drink. He went to a room at the back and returned with a glass of what looked like water. His movements were stiffer than mine. We touched glasses. You could see my jaw muscles tense. Then I checked my watch again.