"The creak of a stair that had not creaked before; the rustle of a shutter when no wind was blowing; the car with a different number plate but the same scratch on the offside wing; the face on the underground that you know you have seen somewhere before: for years at a time these were signs he had lived by; any one of them was reason enough to move, change towns, identities. For in that profession there is no such thing as coincidence."