When an unknown black poodle inexplicably explodes in philosophy professor Timothy Chesterton-Brown's back yard—paralyzing the professor and killing his guest—the "mystery of the sardine" begins. Its solution will involve such unwitting detectives as a twelve-year-old mathematician, his mother, his beloved, a palmist named Miss Prentice, and a bureaucrat dubbed the Minister of Imponderabilia.

The clues they unearth—drawing on logic, the occult, intuition, and everything in between—lead them far away from the tiny seaside town where they begin. We follow them to Majorca, Rome, Warsaw, and London, but in the end, the solution lies beyond even the furthest and most magical reaches of reason.