Everyone in London knows that the lovely Clarinda Humphreys cannot be married before her sister, Jane. But no man dares to court the sharp-tongued spinster, despite the large dowry her desperate father is willing to provide. Randolph Masters, army captain and a viscount, finds Jane unusual and refreshing. Intrigued, he decides to take on the challenge of wooing her. As a last resort, Jane tries to dissuade him by disguising herself as a man and engaging him in a duel. Though she manages to wound him, Masters wins the duel, unmasks her and claims her hand in victory. Then he discovers that his real task has just begun. Winning her hand turns out to be much easier than winning her affection, as their marriage duel continues.