Margaret Brachen and her guest Rita Malrose, a handsome young widow, are extremely jealous of Mlle. Vivian, the Diver, whom Rupert Brachen, Margaret's husband, and John Hawley, see performing at the Hippodrome. They are indignant when the two men invite the charming diver to perform at a lawn fete which Margaret has gotten up at their country place at Travis Sound. But Rita gets an opportunity to make Hawley suspicious and she puts her plans into execution. Some flowers are sent to Margaret by her husband for a sick friend, but arrive after Margaret has started for the friend's house. Rita sends them to Vivian unidentified, and bribes the messenger boy to drop a handkerchief marked with Brachen's initials in Vivian's room. When Hawley sees the flowers and the handkerchief his suspicions are fully aroused. Rita sends a note to him saying that if he would know Vivian's true character, to watch her house at midnight. She dresses up in some evening clothes belonging to Brachen, who is away, and when Hawley comes to Vivian's house, walks down the front steps in full view, returning then to the Brachen home, thus confirming his worst suspicions. The Brachens and their guest Rita stop at Niagara Falls before returning to the city. One day little Agatha, Vivian's daughter, wanders away and gets into a boat which some boys are playing with by the river. The boat slips from the grasp of one of the boys and is carried into the swift current toward Niagara Falls. Vivian, in Niagara to open her season there, while standing on a cliff above the falls sees the child coming down the river. She throws off her pumps and dives into the water. She has a tremendous struggle fighting the current, and only by supreme effort succeeds in getting the boat before it goes over the falls, and taking the child from it to the shore where she falls in a dead faint and is taken to the Brachen cottage to be given medical attention. Rita, repentant, wires for Hawley, and tells him of her duplicity. Hawley rushes in to Vivian, to be reunited with the girl he thought had been false to him.