Two men claiming to be scientists arrive in Colorado looking for Blair, a fellow scientist who disappeared while developing a death ray. The men hire Pete, who finds Blair living with his daughter on a ranch in an inaccessible valley near the Grand Canyon, where the scientist is testing his ray on birds and wild animals. Pete then discovers that the two men from the East are, in reality, agents of a foreign government, who hope to steal Blair's invention. Pete quickly sides with Blair, defeating the foreign agents with the help of Blair's daughter, whom he comes to love. Pete hands the agents over to law officers and returns to the ranch in Lost Valley.