When newly weds Jack and Peggy face eviction, they are tricked into buying a run down houseboat. After rebuilding the engine, they take their friends Sid and Sandra, on a local trip down the river to Folkestone, but somehow they end up in France, and with no fuel and supplies, they resort to desperate actions to get back home.

Edward Lionheart (Vincent Price) stars as an actor overlooked for a critics' acting award, despite producing a season of Shakespeare plays. After confronting the Critics' Circle, an attempted suicidal dive into the Thames results in Lionheart being rescued by your typical paraffin/meths/turps swigging tramps. Lionheart then (presumed dead) exacts his grizzly, and quite amusing revenge on the critics who denied him his finest hour.

Louis Mazzini's mother belongs to the aristocratic family D'Ascoyne, but she ran away with an opera singer. Therefore, she and Louis were rejected by the D'Ascoynes. Once adult, Louis decides to avenges his mother and him, by becoming the next Duke of the family. Murdering every potential successor is clearly the safest way to achieve his goal...