During the 1823 expedition to Spain, the narrator attends a lively ball in Tours where an eccentric, poorly dressed man recounts a dramatic tale to a small gathering. The man, formerly a chief surgeon in the French army under Murat, recalls an episode in occupied Madrid. One evening, he was abducted, blindfolded, and taken to an imposing palace by a disguised lady's maid and an armed lover. In total secrecy, right next to the room of the woman's sleeping, furiously jealous husband, the doctor delivered her deceased child and tended to her critical condition without uttering a sound. Although initially marked for poisoning to safeguard the secret, the surgeon earned the lover's gratitude and was rewarded with gems, though his servant later stole them. However, while indiscreetly narrating the event to French comrades at a subsequent palace gala—describing a distinct birthmark on the woman's arm—a mysterious Spaniard spied on them from the bushes. Soon after, the maid rushed to alert the surgeon before dying from poison. That same night, the shadowy Spanish husband crept into the doctor's room, drugged his guards, displayed the woman's freshly severed arm bearing the birthmark, and stabbed the surgeon in the chest. When an incredulous listener at the ball questions how he survived to tell the tale, the storyteller explains the blade glanced off course. Just then, the surgeon blanches and vanishes as an exiled Spanish grandee enters the reception with his wife, who has lost her right arm.