An American pilot is shot down over Nazi-occupied France and is taken to a convent by the Resistance. The young novice nun Clothilde is interested in him and is willing to help him escape to England, but the pilot must continue his mission undercover by posing as the husband of a different woman.

A young alien falls for a pretty teenage Earth girl and they team up to try to stop the plans of his invading cohorts, who intend to use Earth as a food-breeding ground for giant lobsters from their planet.