Before Jor-El discovered the Phantom Zone, Kryptonian criminals were sentenced to spend their lives in suspended animation, in orbit around Krypton. In the years since Krypton's destruction, one such villain has finally found his way to Earth. The Challengers of the Unknown arrive at the offices of the Daily Planet, looking for Jimmy Olsen. Clark Kent enters and asks if he can be of assistance. The Challengers of the Unknown are looking to contact Superman. Professor Haley tells the story of a bank executive who was poised to leap to his death from the 12th story window ledge of the bank. The Challengers of the Unknown took a multi-level approach to rescuing the man. Red Ryan scaled the building, from the ground up. Ace Morgan, with Haley, piloted a helicopter. Rocky Davis went to the window, and tried to talk the executive off the ledge. Davis held the executive's attention, while Ryan and Morgan moved into position. Haley exited the helicopter on a rope ladder and began swinging towards the executive. With Haley dangling in front of the executive, Ryan grabs the man''s leg. Held in place by Ryan, the executive is dragged back inside the building by Davis. However, once inside, a police officer inquires about a strange card left in the man's office. Upon seeing the card, the executive leaps, in terror, out the window, dislodging Ryan from the wall. Ryan quickly grabs ahold of Haley's legs, and both men work their way back inside the helicopter.
As the card is etched with a Kryptonian symbol, the Challengers of the Unknown are in need of Superman's assistance to solve the mystery. Seeing the symbol on the card, Kent, as Superman, heads to his Fortress of Solitude to probe his memories. The card belonged to the criminal, Zo-Mar. With it, Zo-Mar was able to enslave the minds of any who saw the symbol. General Dru-Zod was able to wrest the card from Zo-Mar's grasp, ending Zo-Mar's siege of Fort Rozz. Zo-Mar was sentenced to a lifetime in incarceration, placed in suspended animation, then launched into orbit. Superman carries the Challengers of the Unknown to the card's origin point on earth. There he encounters Zo-Mar, who uses the card to enslave the Man of Steel. The Challengers of the Unknown, as it turns out, have been in thrall to Zo-Mar the entire time. Zo-Mar demands Superman reveal the secret of his powers on Earth. Superman informs Zo-Mar that his powers are a result of his exposure to the sun's yellow rays. He has no idea why Zo-Mar, a fellow Kryptonian, shows no evidence of possessing the same powers. Believing Superman to be lying, Zo-Mar orders the Man of Steel to destroy a nearby town. Superman is helpless to resist Zo-Mar's commands, and sets about destroying the town. Using his power of super-ventriloquism, Superman issues commands to the Challengers of the Unknown in Zo-mar's voice.
The Challengers of the Unknown are ordered to attack Zo-Mar, and also to refuse any commands that come directly from him. Attacking from all sides, the Challengers of the Unknown are able to overpower Zo-Mar, as Davis wrests the card away from him. With the card in Davis' possession, Zo-Mar's hold over Superman and the Challengers of the Unknown is broken. Suddenly, Zo-Mar's Kryptonian powers manifest. Superman surmises that, in some way, the card must have been preventing Zo-Mar from developing powers under Earth's yellow sun. Superman and Zo-Mar battle it out in the sky, above the Challengers of the Unknown. Zo-Mar begins firing bursts of energy from his hands, a power Superman has never possessed. Superman uses his super-breath to draw the card from Davis' hand. Superman then blows the card towards Zo-Mar. The moment Zo-Mar touches the card his powers vanish. Superman, moving at super-speed, punches Zo-Mar into unconsciousness before he can use the card to enslave the Man of Steel once more. Zo-Mar awakens in the Phantom Zone, where he is greeted by Jax-Ur and, surprisingly, Zod. The Challengers of the Unknown return to the Daily Planet offices, and again inquire about contacting Jimmy Olsen. Once again, Kent enters the room and asks if he can be of assistance. The Challengers of the Unknown are looking to contact Superman again, to clear up some questions they have regarding Superman's battle with Zo-Mar. Kent challenges them to find their unknown answers on their own.