For the briefest of instants, his mind was a blank. He knew the details of the present moment: he was climbing a dark, narrow staircase; the air was warm and close, sour-smelling; his right temple ached. But none of these facts gave him any clue to where or when this was happening, or even to his own identity.

He stood still, breathing heavily, and a hundred vague staircases swam together in his memory. Had he been here before? It looked familiar, but then a staircase was a staircase. That smell reminded him of something, though. What was it? Rotten vegetables, he thought. Uncollected refuse. Human faeces. He listened closely and heard the faint hum of traffic; someone coughing from behind a door.

Suddenly, unbidden, a series of quick, hazy images flashed through his mind. Seconds later, they had vanished, and he was left with no remembrance of them except for one: the vague, half-turned-away face of a dark-haired girl. As far as he could tell, she looked young and beautiful, but he had no idea who she was, or why she had entered his mind. He felt sure he had never seen her before. For some reason, however, the sight of her face filled him with a strange emotion. It was, he thought, an emotion without a name: whatever it is that exists on the border between hope and fear.

For a moment he was breathless, suspended in time, and then a drop of sweat trickled down his forehead and into his eye. It stang. He blinked. And, in the second that it took for his eyes to close and reopen, it all came back to him.

Reality. The present. His self.

His name was James Purdew. He lived in Amsterdam, in an apartment he shared with his Dutch girlfriend, Ingrid. He had just come back from work to make himself a sandwich. It was lunchtime on Monday 7 July; the day before his thirtieth birthday.

Relieved, he began climbing the stairs again. All in all, the blackout could not have lasted more than a few seconds. He had no idea what had brought it on -- a momentary break in the supply of oxygen to his brain? -- but he felt sure it was nothing to worry about.

Halfway up the stairs, he heard a harsh, urgent, familiar sound. He started to run, taking the steps two at a time. Near the top of the third flight, he missed his footing, slipped, and felt a small crack. Still the sound continued, high-pitched and imperative. The pain was horrific, but he managed to climb the last few steps, unlock the door of the apartment and crawl towards the telephone. It had stopped ringing by then, of course. All he could hear was the recent memory of its ringing, like a disturbance in the air.

Even now he remembers vividly the thirty-nine seconds he spent crawling across the sitting-room floor, though naturally it seemed to him to take much longer than that. He remembers sweat dripping from his forehead on to the smooth, pale floorboards, and resting there in perfect little pools. He remembers the sound of blood beating in the veins inside his eardrums. He remembers how strange and distant the ceiling appeared from his position on the floor. Or, at least, he remembers remembering these details; the pictures themselves quickly faded, as all such pictures do, and he is forced to reimagine them -- to invent them anew -- whenever he tries to bring to mind the events of that fateful day.

The first thing he did when he reached the telephone was to check the answer machine. One message. He played it: nothing but a staticky hiss followed by a long beep. He listened to the message again, searching for clues, then he dialled 9293, but the caller had suppressed their number. With an odd feeling of guilt, he erased the message.

Only then did he call for an ambulance.

* * *