Sir Percy Blakeney (Anthony Andrews) is a English aristocrat who leads a band of his peers (the League of the Scarlet Pimpernel) into France during the French revolution, attempting to spirit out of the country the potential victims. Back in England he poses as a fop, making himself a subject of ridicule lest his identity be guessed. He falls in love with and marries a French actress, Marguerite St. Just (Jane Seymour), but when he hears that she denounced an entire family to the guillotine (because her brother was beaten for loving the family's daughter), he no longer trusts her and their marriage becomes cold.
The Revolutionary government sends an agent to hunt down and kill the Scarlet Pimpernel. The agent, Chauvelin (Ian McKellen), is an old flame of Marguerite's and when she refuses to leave Percy for him, he in turn black mails her with the information that her brother is in the League - if she does not help discover the identity of the Scarlet Pimpernel, her brother will go the guillotine. Marguerite helps, giving Chauvelin a piece of correspondence from one of the League members, but racked with guilt, she goes to where the correspondence says the Pimpernel will be and tells the man (Percy, hidden in the shadows) what she has done, and begs him to save her brother. She tells him that it was Chauvelin, a friend she had told in confidence, who had denounced the family to their deaths. She leaves not knowing Percy's identity, but when he disappears (going to rescue her brother), she figures it out.
Chauvelin, now armed with the knowledge of the Pimpernel's identity, goes back to France to foil Percy's attempt to free the Dauphin. In the end, both her brother and the Dauphin are saved. Percy is captured and Marguerite helps to get him out of jail. Chauvelin is defeated and left to face the wrath of the Revolutionary government. Percy and Marguerite reconcile and sail back to England.
Thanks Mary C!