May, twenty years old, and Bessie, six years old, live with their grandfather, an old recluse and bookworm. May is invited to a dance by Jim, the ne’er-do-well son of Mrs. Heap, the housekeeper. May dislikes Jim and is not inclined to go, but her grandfather persuades her to accept the invitation. Bessie has made a pet of a white mouse and shows it to her grandfather who smiles absently and returns to his books up in the garret. While at the dance. May is insulted by a bully. Bob, a stranger, knocks the bully down. Jim, who fears the bully, is angry at the turn of affairs. May shows her contempt for him by accepting Bob’s invitation to take her home. The two fall in love with each other. Mrs. Heap discovers the hiding place of the old man’s gold. Filled with greed, she takes her son and the bully into her confidence. They plot to steel the money. May goes out with Bob the following night. During their absence, Jim and the bully overpower the old man. Bessie enters the room and is warned to keep silent. The little girl scrawls a note calling for help, pastes it on the back of the mouse which she then shoves into the mouth piece of a speaking tube leading to the lower part of the house. May returns home and sees the mouse peeking out of the tube. She pulls it out and finds the call for help. She summons Bob who is talking with a policeman and they return to the house. Jim and the bully are about to escape when captured by Bob and the officer. Bob releases the old man and then tells of his love for May. In gratitude, the grandfather gives his consent to their engagement.