At the base of a tall building, Speed and company watch Twinkle Banks, star of the Universal Circus, dive off the top. Then, at the circus, they watch Twinkle drive a racecar and perform daredevil stunts. She worries about maintaining the car's momentum and faints. Speed rescues Twinkle. While the girl daredevil rests in bed, a clown (her father) tells Speed that because of a money shortage, he's having difficulty keeping the track in good repair. Speed makes a donation. Later, Speed and Trixie learn on the radio that Twinkle will drive a car, balanced on two ropes, over Niagara Falls. Because of the strong winds Speed and Trixie try to stop Twinkle.

Meanwhile, Cornpone Brush, who financed the stunt, tells the clown that Twinkle will perform regardless of the hazardous weather. When Speed and Trixie arrive, Twinkle is already making her way across the Falls. Away from the crowd, Brush reads an old map. It identifies a secret cave in back of the Falls that leads to treasure.