Gertrude, living with her father, the keeper of the light, loves Ned, but is betrothed to John, who has just returned from a long absence. John is bitten by a mad dog and hydrophobia develops. Ned's ship is on the way to the island, and John, knowing this, fails to turn on the light. Gertrude and her father are away. They return and John fights the old man to prevent his turning on the light. They struggle on the stairs and John falls and is killed. Gertrude is trying to light the lamp. She calls her father to her aid. Duty prevails over his grief and he responds. Ned's ship is saved.