Doctor Darrk invented a portable ray that could make things invisible and, with his two assistants, Butch and Nan, used it to steal valuables. In his secret identity as chemist, Rex Tyler, Hourman became suspicious of the amount of chemicals ordered by Doctor Darrk, and investigated secretly, but was spotted by Nan, and knocked out by Butch. After changing to Hourman and taking his miraclo pill, Hourman destroyed Darkk's super-robot, Giganto, and eventually captured Darrk, Butch and Nan.
