Sheila Gray is preparing for a date when her mother Mrs. Gray comes in with flowers from her new suitor, Henry Mallory. Her daughter insists that she hates Henry, who has something wrong with him, and she plans to marry John Coolridge. Henry has also sent a present and said that she has to wear it. It’s a brooch of a small mouse-like creature, and Mrs. Gray pins it on her daughter’s lapel.
They go downstairs and Henry says that he’s taking Sheila to an expensive restaurant for dinner, and has hired a car. Mrs. Gray is overwhelmed but her daughter is less than impressed. They go to the restaurant and Henry asks how many times that they’ve gone out without her asking about him. Sheila asks him and Henry says that he’s the only child of a widowed mother like her. At an early age he set out to become the best at everything and succeeded. Henry knows that she plans to marry John, and suggests that she change her mind. Sheila refuses, insisting that she’s in love, but Henry warns that it never lasts and being a good husband is what matters. He tells her that she’ll never marry John, and Sheila says that they’ll see.
Henry then goes to her coat, hanging nearby, and explains that it represents a kind of mouse similar to a bat. He removes the brooch pin and the creature sticks to the coat. Sheila points out that he talks about it as if it were alive, and Henry admits that he’s being foolish. She gets up to leave, and Henry gives her one last chance to change her mind. He says that he likes her the best of the other girls that he’s had, but she declines.
Henry pays the chauffeur to go home for the night. As he drives Sheila home, she says that Henry will make a good husband for some girl, but she loves John. When Henry dismisses John as a peacock, Sheila takes offense but he suggests that they go gambling. She refuses and says she wants to go home, and Henry pulls off onto the side of the road. He grabs her and kisses her, and she gets out of the car despite the fact that it’s three miles back to the town. As Sheila goes, Henry says that she’s made her choice and he’ll remember her as she was: beautiful and deserving.
Once Henry drives away, Sheila starts walking along the road. She cuts across the countryside and adjusts her collar, and pricks her finger on the brooch. When she touches it again, she bleeds from her finger. She tries to run away, throwing it off, but the creature grows larger. When she trips, it crawls up her coat to her face.
A while later, two men, Frankie and Gippo, are bicycling home when Frankie sees something crossing the road ahead of them, something like a hedgehog covered in blood.
Henry goes to a bar and flirts with the girl sitting next to him.
Frankie and Gippo continue along and find Sheila’s corpse, it’s face ripped apart.
Henry gives the girl a mouse-shaped brooch as a token of his appreciation. She warns that it doesn’t mean anything, but Henry simply smiles and places it on her lapel.