The only character central to the investigation and thus to the novel is the protagonist. The Chain of Chance purports to be a book written by the hero as a post facto record of the events (as we find out on the very last page). Considering his focal position in this first-person narrative, it is striking that in many ways the hero remains an enigma even when the book has ended. Of course, we know something of his physical characteristics since he is chosen for the "simulation" mission precisely because he matches the victims in appearance. His composite portrait, assembled during the interview with Professor Barth, is as follows: single, male, in his fifties, tall, athletically built, does not have diabetes, and suffers from allergies.

But even in this very incomplete picture some blank spots linger. The precise age of the protagonist seems difficult to determine, since at...