At the home of General Sir Joshua Blazes his daughter Millicent and other ladies are making comforters for the British soldiers in the Crimea. The General and the Prime Minister, however, are concerned that the war is not going well because of the disappearance of secret papers into the hands of a spy known only as The Unknown Terror. Little do they suspect that he is Captain Rudolph de Vavasour, who has watched them hiding the latest documents in a plant pot, and comes out to purloin them when they have left. He then woos (unsuccessfully) Millicent, who prefers Launcelot Brown. When the latter is accused of removing the papers, he claims to have been alone in the room at the time rather than reveal the compromising position in which he discovered Millicent, and is cashiered. Two years later Millicent is preparing to marry Vavasour when Brown, who has been away in Russia discovering the truth, turns up and exposes him. He is executed, while Millicent switches her attention to Brown, the Pride of the Regiment.