The film follows Jack Hopkins (played by Michael Craig), an aircraft designer with a passion for traction engines. His boss (played by Cecil Parker) is eager to sell a new supersonic jet plane that Jack has designed to American millionaire Paul Fisher (Alan Hale, Jr.). The first encounter between Fisher and Jack goes badly, and tensions only heighten after Fisher's daughter Kathy (Anne Helm) damages Jack's prize traction engine "The Iron Maiden", rendering it impossible to drive solo. Jack is desperate to enter the annual Woburn Abbey steam rally with the machine, but his fireman is injured and unable to participate. When all seems lost the millionaire himself is won over by Jack's plight and joins him in driving the engine; the two soon become firm friends.
In and around the castle Camelot, brave Cornel Wilde (as Lancelot) and virtuous Brian Aherne (as King Arthur) vie for the affections of lovely Jean Wallace (as Guinevere).
A pretty young woman will do anything to escape her deadly dull existence in the backlots of Wales. But when she reaches the bright lights of London is the price too high?
An up and coming politician is caught in a compromising photograph taken by a maid, who turns out to be part of a sophisticated blackmail ring. When the girl is found murdered, he holds an incriminating old dueling pistol.
The story of the conception of a new British weapon for smashing the German dams in the Ruhr industrial complex and the execution of the raid by 617 Squadron 'The Dam Busters'.
