As the headline on the Daily Planet tells the public: “Mechanical Monster loots bank!” In fact, a scientist has an army of these flying robots able to steal anything in sight. Police are set up everywhere to guard an exhibition of rare jewels, but it’s no use. When a robot crashes into the building, it steals all the precious stones in sight, while the policemen’s bullets harm it no more than flies. Clark and Lois are at the exhibit. While Clark phones in the story from a booth, Lois stows away in the robot’s compartment. Clark sees that Lois has gone missing and decides to change into Superman there in the phone booth. Superman follows the monster, while his X-ray vision allows him to spot Lois inside. His attempt to get Lois out fails. The robot knocks him onto some power lines, losing the jewelry and (nearly) Lois in the process. The robot returns to the scientist’s hideout with Lois, but no jewelry. She refuses to tell the scientist where it is. He retaliates by tying her up and setting her on a platform over a pot of boiling metal. The platform slowly descends, as Superman breaks in. But he’ll have to fight the scientist’s entire army of robots to save the day.