A group of children fleeing Napoleon's armies attempt to protect a mountain escape route from being discovered by a pursuing French platoon.

Bumbling navy officer Lieutenant Humphrey Fairweather (David Tomlinson) is transferred to HMS Berkeley, an old World War II destroyer, to keep him out of harm's way. But together with Chief Petty Officer Doherty (Peter Sellers), Fairweather gets into more trouble than might be thought possible, with events coming to a riotous conclusion when the Admiralty turn up for an inspection of the ship.