Dirty Tricks

When the nameless narrator embarks upon an affair with Karen, a seemingly vapid P.E. teacher married to a boring accountant, he does not know her fetish is for adultery while her husband is in the room or loitering nearby. But once he finds out, he doesn't care. He has been abroad for twenty years, and since his return to merry old England he's been startlingly uninhibited by morals or a conscience. Which is not only why he eventually gets involved with blackmail, a kidnapping, and two murders, but also how, with hilariously syllogistic logic, he's able to justify his role in all of it.