During Carnival in early-20th-century Spain, the boulevards of Seville thrum with life as revelers in grotesque costumes and masks fill the streets. A detachment of Civil Guards staggers through the masquerade, adding a sharp note of danger to the festive chaos. Antonio Galvan, Cesar Romero, a young bourgeois revolutionary just back from exile in Paris to visit his parents, blends with the crowd while deftly dodging the authorities in pursuit. He locks eyes with the dazzling Concha Perez, perched on a float, and she slips away into the sea of revelers with him in pursuit. A message arrives for Antonio—an invitation to meet Concha that evening, a chance to see if the spark between them can ignite into something more.
As the tale unfolds, Antonio encounters his old friend Don Pasqual, Lionel Atwill, a middle-aged aristocrat and former Captain of the Civil Guard. Pasqual senses the danger of Antonio’s attraction to Concha and uses a string of flashbacks to tell the story of how Concha wrecked his life. He recalls how she helped him when she left a cigarette factory job and how his ardor nearly bound him to her forever. He proposed, she disappeared, and when she returned months later, she asked for money while insisting that she loved him. He offered again, but she rejected him. Eventually, Pasqual did win her, buying out her contract so they could be together, only for her to leave again—with a young bullfighter—leaving his reputation in tatters and causing him to resign in disgrace.
Although Antonio vows to steer clear, he cannot resist Concha. They slip away to a nightclub, where he hopes to exact revenge for Pasqual, yet he remains unable to resist her allure. A letter arrives for Concha from Pasqual, sent with a plea for a reunion and a declaration of undying love. She reads the letter to Antonio, and his fury grows as he realizes Pasqual has misled him. When Pasqual bursts into their private room, Antonio accuses him of lying to outflank him, and Pasqual demands that Antonio leave town. The tension erupts into a duel, and Pasqual calmly demonstrates his marksmanship before taking his leave.
Concha makes a bold pledge to accompany Antonio to Paris after the duel, and Antonio begins writing farewell letters. The next morning, Pasqual and Antonio meet at a secluded spot where Concha bluntly reveals that if he ever truly loved her, he could not kill the man she has cared for. As the duelists stand at their marks, Pasqual fires a shot into the air—an act that goes unnoticed by Antonio until the fatal moment. Antonio’s gun replies, and Pasqual is gravely wounded. Police arrive to arrest the fugitive Antonio, and Pasqual is taken to the hospital as Concha’s future hangs in the balance.
With Antonio imprisoned, Concha turns to Governor Paquito, Edward Everett Horton, to secure his release. He reluctantly issues two passports so Concha and Antonio can slip away to Paris. Before reuniting with him, Concha visits Pasqual in the hospital to thank him for sparing Antonio’s life. Pasqual accepts that his action was an act of love, yet he cannot forgive her, and she leaves with a heavy heart but a sense of resolve. The couple finally makes for the French border, passing through customs with ease. Their train car waits, and Antonio eagerly steps aboard, only to watch as Concha hesitates at the station master’s side. When she speaks at last from the moving train, she reveals that she will not board and that she has chosen to rejoin Pasqual, leaving Antonio to watch the landscape blur into a future unlived.
