In October 1941 Doctor Robert Crane and his assistant Doctor Chuck Grayson are putting the finishing touches on their latest creation, a mechanical man, which they have designed to keep alive a human brain whose owner has died. Without knowing any specifics, some hoodlums break in to steal whatever the top-secret project is. When Dr. Crane tries to stop the crooks he is shot dead. The thieves, mistaking the robot for a statue, finds nothing else of value and escape into the night. With his dying breath, Crane instructs Grayson to put his brain into the robot body. After the operation the mechanical body housing Dr. Crane's brain sleeps. The police arrive and arrest Grayson for Dr. Crane's murder! Awaking, Crane creates a human mask and assumes the new identity of Paul Dennis. Finding his killers and bringing them to justice, Crane effects the release of his friend, Dr. Grayson. After attending the funeral for Robert Crane, Paul Dennis gets back together with his girlfriend, Joan Carter. The mechanical man dedicates himself to crime fighting as Robotman!

    In addition to his great mechanical strength, Robotman has exceptionally acute senses thanks to photoelectric eyes and microphonic hearing, and his robot legs can generate several hundred horsepower worth of speed. But Robotman can get rundown if he overexerts himself, and he must recharge his generator when necessary. In later years he creates a sentient talking robot dog Robbie to aid him in his battle against evil. Robbie wears fake fur over his metallic frame when Robotman is in his secret identity of Paul Dennis. Robotman has a very long and successful career championing good and righting wrongs.