A self-assured businessman murders his employer, the husband of his mistress, which unintentionally provokes an ill-fated chain of events.
Four prison inmates have been hatching a plan to literally dig out of jail when another prisoner, Claude Gaspard, is moved into their cell. They take a risk and share their plan with the newcomer. Over the course of three days, the prisoners and friends break through the concrete floor using a bed post and begin to make their way through the sewer system -- yet their escape is anything but assured.
Henry Roubier, a French promoter, and Enrico Mazzini, an Italian, have signed an agreement guaranteeing them a stranglehold on European highways. While driving on the roads of the south, Roubier takes two young hitchhikers, but an unfortunate swerve the car rushes by Henri and its occupants on the top of a pine tree onto the side of a cliff.
