The master crook steals the sweetheart of Sherlock, a great detective. Sherlock undertakes to recover her. The crooks make futile attempts on his life and then to lure him to their den, they drag the girl at the end of a rope tied to an automobile. Sherlock chases it, catches the girl, and while she is trying to untie the rope, he holds the auto by strength. The auto and he pull and the rope parts in the middle. Sherlock falls over while the auto plunges over the end of a pier. It sinks to the bottom where the crooks strip the tires off, and using them as life preservers, come to the top, just as the master crook pushes the girl into the water. Sherlock blows his police whistle and the motorboat cops start up. Sherlock, in casting off the rope that ties the boat to the dock, gets tangled in it and is dragged through the water after the boat. The crooks and the girl flee in a rowboat. The motorboat cuts through the frail craft, throwing the crooks and the girl into the water. As Sherlock comes by at the end of his rope, he grabs the girl and they climb into the motorboat and are save. They leave the crooks struggling in the water.