A thief named Icy Harris tries to steal a rare isotope called Galaxy 4, but it explodes in his face. When security guards try to apprehend him, he finds out the isotope has given him the power to absorb the strength of anyone nearby.
When Clark Kent tries to stop him from escaping from the scene of a robbery, Harris absorbs so much strength from him he realizes Clark must really be Superman in disguise! Superman manages to get away, but Harris wants all of Superman's power for himself. He schemes to lure Superman out into the open, first by throwing a missile at the Washington Monument and then a small plane at a passenger jet.
Superman averts these disasters and indeed confronts Harris again, and realizes the only way to defeat Harris is to give him exactly what he wants. Superman lets Harris absorb all of his powers, but because his body contains all of Superman's power without also having Superman's invulnerability, Harris explodes.