Paula (Jacqueline Logan), a leopard trainer known as the Leopard Lady, is hired by police to join a circus and investigate a series of thefts and murders. She discovers that Caesar (Alan Hale), a Cossack, owns an ape trained by him to be a vicious killer. At first the Leopard Lady hesitates to expose Caesar because he once saved her life. Later, when the ape almost kills her fiance, she reveals the truth and sends for her chief to make the arrest.