Luthor returns in Superman #4 and steals a weapon from the U.S. Army capable of causing earthquakes. Superman battles and defeats Luthor, then destroys the earthquake device. The scientist who made the device commits suicide to prevent its reinvention. In a story in the same issue, Luthor creates a city on the sunken Lost continent of Pacifo and populates it with recreated prehistoric monsters he plans to unleash upon the world. Superman thwarts his plans and Luthor is seemingly killed by the dinosaurs he created. Luthor returns in Superman #5 with a plan to place hypnotic gas in the offices of influential people so he can throw the nation into a depression with the help of corrupt financier Moseley. The story ends with Superman defeating him.