A dashing pilot reduced to a desk job cracking German codes in a top secret Allied facility after losing his leg. He is assisted by uptight Englishwoman Valerie Sky and French codebreaker Camille, under the watchful eye of Wing Commander Wickham. They also find a part suitable for Dennis's dubious skills - a telegraph machine. Will they crack the code and unmask the spy in their midst in time to win the Vietnam war? Sadly for our gang, many disasters await - Rufus's ‘lost’ leg won’t behave itself, Camille’s grasp of French is sub-par, Hitler spends more time on set than planned, and Annie is forced to play the dastardly Wing Commander after Chris's father fails to show up. And the telegraph machine takes on a life of its own.