Action Comics #42 (1941)

Action Comics #42, also known as "The Empire in the Sky," follows Clark Kent as he investigates a series of disappearances in Metropolis. When he discovers that one of the missing men, scientist Carl Bransom, has been kidnapped and a ransom has been demanded, he realizes that it's a job for Superman! As Superman, he captures the man picking up the ransom, only to watch him suddenly get destroyed by a mysterious death ray from the sky. Superman soon finds himself on a floating sky city where he discovers the missing men. But this floating city is not what it seems when he meets the leader, who claims to be an extraterrestrial named Zytal. Later, Superman learns that Zytal is actually Luthor in disguise, who has been using the city to learn the men's secrets and then kill them. Luthor even manages to hypnotize Superman using electricity! But fear not, for Superman eventually overcomes Luthor's hypnotism and saves everyone. Other stories in this comic include the first appearance of the Vigilante and stories featuring Black Pirate, Three Aces, Mr. America, Congo Bill, and Zatara. Keep in mind that if you have this issue in your collection, it could be quite valuable!