Death in a French Garden is a story about a magnate and his younger wife who hire David to teach guitar to their teenage daughter. The wife quickly seduces David, while he strikes up an acquaintance with the family's inquisitive neighbor.
One night, David is mugged but rescued by a stranger named Daniel, who admits to being a hit man and becomes David's friend. Video tapes of their activities start appearing in the lovers' mail, leading to suspicions and paranoia.
David believes the tapes are from the neighbor, while Daniel is convinced that the husband is aware of the affair and hired the mugger. When Daniel reveals that he has been hired to kill the husband, an elaborate manipulation unfolds, involving murder, suicide, a payoff, more videos, and a surprising twist in the end.