Bumbling navy boffin Lieutenant Humphrey Fairweather is disciplined after his pet guided missile project goes awry and he blows up a fellow officer's bathroom. The top brass decide to stick him where he can do no more harm, in charge of the mothballed destroyer HMS Berkeley. However, due to a typical navy oversight, HMS Berkeley hasn't had a commanding officer for over three years, and its crew are now used to a cushy way of life. Led by Chief Petty Officer Docherty, they've converted their ship into a highly profitable farm, laundry and bakery and are now making a fortune selling off excess naval rations and supplies to the local village! At first, poor Fairweather hasn't a clue about what's going on all around him, but as the truth starts to dawn he suddenly finds himself an unwilling accomplice. Of course, that would be the moment when the Admiral decides to make a snap inspection...