In one part of town, a woman robs a bank. In another, a corpse is found shot through the heart in a room locked from within, with no firearm in sight. Although the two incidents appear unrelated, Detective Inspector Martin Beck believes otherwise, and solving the mystery acquires the utmost importance. Haunted by a near-fatal bullet wound and trying to recover from the break-up of his unhappy marriage, Beck throws himself into the case to escape from the prison that his own life has come to resemble.