Their long-awaited, happily started vacation of old friends on the Black Sea coast is interrupted by the murder of their new acquaintance. Anton Snezhin, a professional mathematician and bridge player, has to sort out a complicated and dangerous “solitaire.” Criminals, detectives, cunning and a bit frivolous women, a psychotechnician and a business consultant, a scientist, an official, and even an amateur psychic—each will take their place in this game. Everyone has their own motives: some seek power and profit, others want to restore legality, still others are drawn to pleasures. But love will win.