Description
At the Central Park Zoo in New York City, Serbian-born fashion illustrator Irena Dubrovna (Simone Simon) makes sketches of a black panther. She catches the attention of marine engineer Oliver Reed (Kent Smith), who strikes up a conversation. Irena invites him to her apartment for tea. At her apartment, Oliver is intrigued by a statue of a medieval warrior on horseback impaling a large cat with his sword. Irena informs Oliver that the figure is King John of Serbia and that the cat represents evil. According to legend, long ago, the Christian residents of her home village gradually turned to witchcraft and devil worship after being enslaved by the Mameluks. When King John drove the Mameluks out and saw what the villagers had become, he had them killed. However, "the wisest and the most wicked" escaped into the mountains. Oliver is dismissive of the legend even though Irena clearly takes it seriously.
Oliver buys her a kitten, but upon meeting her, it hisses. Irena suggests they go to the pet shop to exchange it. When they enter the shop, the animals go wild in her presence, and Irena becomes uneasy. Irena gradually reveals to Oliver that she believes she is descended from the cat people of her village, and that she will transform into a panther if aroused to passion. Despite this, Oliver asks her to marry him, and she agrees. However, during the dinner after their wedding at The Belgrade, a Serbian restaurant, a cat-like woman walks over and addresses Irena as moya sestra ("my sister"). Irena never consummates the marriage, fearful of the consequences. Oliver is patient with her, but eventually persuades her to see a psychiatrist, Dr. Louis Judd (Tom Conway). Judd tries to convince her that her fears stem from childhood traumas. Meanwhile, Irena is unhappy to discover that Oliver has confided in his assistant, Alice Moore (Jane Randolph). Alice confesses to Oliver that she loves him. When Irena chances to see Oliver and Alice seated together at a restaurant, she follows Alice home. Just as Alice hears a menacing sound, a bus pulls up and she boards it. Soon after, a groundskeeper discovers several freshly killed sheep. The paw prints leading away turn into imprints of a woman's shoes. Irena returns to her apartment looking dishevelled and exhausted; she is shown shortly afterwards weeping in the bathtub. Irena dreams of Dr. Judd dressed up as King John speaking of "the key". She later steals the key to the panther's cage in Central Park.
Irena, Oliver and Alice visit a museum, and Irena is angered when the two virtually ignore her. That evening, when Alice decides to use the basement swimming pool of her apartment building, she is stalked by an animal. When Alice screams for help, Irena appears, turning on the lights, and says she is looking for Oliver. Alice later finds her bathrobe torn to shreds. After an appointment with Dr. Judd, Irena tells Oliver that she is no longer afraid, but Oliver tells her it is too late: he has realized that he loves Alice and intends to divorce Irena. Later at work, Oliver and Alice are cornered by a snarling animal. Oliver and Alice manage to get out of the building but not before smelling Irena's perfume. Alice calls Judd to warn him to stay away from Irena, but he hangs up when Irena arrives for her appointment with him. He kisses Irena passionately, resulting in her transformation into a panther who attacks and kills him. When Oliver and Alice arrive at Judd's office, Irena slips away and goes to the zoo. There, she opens the panther's cage with the stolen key and is struck down by the escaping panther, which is accidentally run down and killed by a car. Next to the panther's cage, Oliver and Alice find a dead panther lying on the ground. Oliver says, "She never lied to us."
