Dr Otto Spethmann, the rather self-important narrator, is a psychoanalyst, a widower with a wilful 18-year-old daughter, and a keen amateur chess player involved in a long-drawn-out game with a friend, the Polish violinist R M Kopelzon. He finds in Rozenthal's play, he tells us apologetically, "something of the decisive, organic simplicity of a Mozart clarinet concerto". His patients include a young revolutionary, a sex-obsessed clerk at the foreign ministry and a society beauty called Anna Petrovna . . . daughter of a selfmade entrepreneur and reactionary ideologue known as the Mountain . . . with whom he is more than a little infatuated. He is also seeing Rozenthal. The eccentric, almost autistic, chess genius is clearly on the brink of a breakdown, but Kopelzon has specifically asked Spethmann to do whatever it takes to enable him to play in the tournament.

This thriller by Ronan Bennett was first published in serial form, and the brilliant set-up is deceptively deadpan. Spethmann is well aware that St Petersburg, "where magnificence and squalor co-exist", is inevitably full of "envy, rage, cruelty, paranoia and violence". But his own calm, apolitical life seems to possess a kind of dull equilibrium. So why have the police found his business card in the pocket of a murdered revolutionary? And why are they so interested in a harmless, unworldly obsessive such as Rozenthal? Can there really be a link between his "ingenious slayings" at the chessboard and the real-life mayhem on the streets?

As Spethmann's stable world starts to unravel, agents reveal themselves as double agents and activists seem willing to kill allies in order to discredit opponents, he is forced to question what he knows even about family and friends. So he falls back on the old chess player's technique of calculating "variations". What will be the result, several steps down the line, of trusting . . . or of not trusting . . . the police?

His problem is not only the immense complexity of such calculations. Perhaps there just isn't a solution and he is in zugzwang, the uncomfortable situation well known to all chess players where every move is sure to lead to disaster. After many attempts, he has finally managed to trap Kopelzon on the board, but what if every path is now blocked to him in real life?

The book includes diagrams of the Spethmann-Kopelzon game which give it an extra dimension for chess buffs. Yet one needs to know nothing of "mysterious rook moves" or the Maroczy Bind to enjoy this atmospheric, ingenious and perfectly paced novel.