Paris, 1792. The Revolutionary tribunal sentences aristocrats to death nightly. A mysterious rescuer — the Scarlet Pimpernel — has already spirited away several condemned families under impossible circumstances, leaving behind a signature red flower.

At the Dover inn, English travelers gossip about the Scarlet Pimpernel's latest rescue. The rescued Comtesse de Tournay and her children arrive safely. We learn of Marguerite Blakeney and her reputation as the cleverest woman in England.

The most recent Pimpernel rescue is described in detail: the St. Just family escapes through an elaborate disguise scheme at the city gates of Paris. The Chapter establishes the League's methods and daring.

Sir Percy and Lady Blakeney attend a reception at the French Embassy in London. Chauvelin approaches Marguerite. Percy is introduced as apparently vapid and ridiculous. The social performance of the English upper class is on full display.

Alone after the ball, Marguerite weighs Chauvelin's demand. She loves her brother Armand above all else. She does not love Percy. She decides she has no choice but to help Chauvelin find the Pimpernel.

At a grand ball at Lord Grenville's, Chauvelin shadows Marguerite and watches the Pimpernel's associates. Marguerite intercepts a message from Lord Hastings that identifies the Pimpernel's next move. She hands it to Chauvelin — and immediately regrets it.

After the ball, Percy and Marguerite return home. In a rare moment of privacy, something almost breaks through between them. Percy is strange and tender before the moment passes. Marguerite is left wondering what she has done and who her husband truly is.

Marguerite discovers a letter from Armand in Percy's papers — written to the Scarlet Pimpernel. The revelation hits: Percy is the man she has just betrayed to Chauvelin. Horror-stricken, she seeks help from Percy's friend Sir Andrew Ffoulkes.

Marguerite tells Sir Andrew what she has done. Sir Andrew confirms Percy has already left for France. Marguerite resolves to follow. She arranges passage and departs for the Channel.

Chauvelin arrives in Calais with soldiers. He sets up surveillance at the Chat Gris inn — the known rendezvous point for the Pimpernel's network. He waits with cold patience for his quarry to arrive.

Marguerite crosses the Channel and reaches Calais. She finds shelter and begins searching for signs of Percy or his associates. The danger of her position — an English woman alone in revolutionary France — becomes vividly real.

Percy, disguised as an elderly Jewish merchant, moves through Calais managing his rescue operation. His disguise is so complete that Marguerite, seeing him in the street, does not recognize him.

Chauvelin's surveillance nets begin to tighten. He captures one of the League members and extracts partial information. He now suspects the old Jewish merchant. He lays an ambush near the coastal road.

Chauvelin's soldiers find Marguerite searching near the coastal road. Recognizing her as Lady Blakeney, Chauvelin takes her into custody — not to arrest her but to use her as bait to draw Percy in.

Brief interlude: The rescued aristocratic family reaches Percy's waiting boat. Percy's League members have successfully moved the escapees to safety. The operation is already half-complete — Chauvelin's trap has closed on an empty net.

Percy receives word of Marguerite's capture. He sends his League associates ahead to safety. Alone, he devises a plan to extract Marguerite and simultaneously elude Chauvelin's soldiers. The masquerade ends.

Percy, in a new disguise, enters the Chat Gris inn where Chauvelin is holding Marguerite. Using a forged document and performance of absolute authority, he creates a diversion that allows Marguerite to be moved — but Chauvelin suspects something.

Chauvelin dispatches soldiers to intercept the Pimpernel at the coastal rendezvous. Percy leads a portion of the soldiers on a false trail through the coastal darkness while his associates bring Marguerite to the waiting yacht.

Marguerite reaches the yacht. Percy, having eluded the last of Chauvelin's soldiers, arrives moments later. They are reunited aboard the Day Dream as it pulls away from the French coast into open water.

The Day Dream sails for England as dawn breaks. Marguerite and Percy speak freely — perhaps for the first time. The mystery of his identity, the truth of her past, the years of misunderstanding: all resolved in the sea air. The novel ends with the coast of England visible ahead.