Superman; Lois Lane; Metallo [John Corben] (intro, villain); Professor Vale; Perry White; Jimmy Olsen (unnamed)
Criminal John Corben, who is nearly killed in an auto accident, is given a robot body powered by uranium. When he is hit by bullets meant for Lois, she assumes he is really Superman. Recognizing a good idea, Corben impersonates Superman to collect more uranium. Running out of sources of uranium, Corben learns that he can also be powered by kryptonite. But he doesn't realize that the kryptonite he steals is fake, prop kryptonite and collapses.
While leading an expedition through the desert, Congo Bill stops at an apparently deserted oasis. But the water has been drugged, and the expedition passes out. When they awaken they find they are prisoners inside a nearby outpost that has been taken over by renegades. Bill, who is imprisoned separately from the others, rubs his magic ring and soon Congorilla is attacking the fort and freeing the expedition.
Superman [Kal-El]; Supergirl [Kara Zor-El] (introduction, origin); Zor-El (introduction, flashback); Miss Hart (introduction); Superboy (on a poster)
Superman spies a crashing rocket and discovers his cousin Supergirl. She tells him how Argo City survived the destruction of Krypton and how her father sent her to Earth when the inhabitants of Argo City were threatened by Kryptonite poisoning. Superman sets her up in Midvale Orphanage so she can adjust to life on Earth.