An alien uses a giant spaceman to absorb disaster-energy in order to make himself invulnerable!
A strange machine has rendered the entire populace of the planet Allamar comatose. Wonder Woman, the Green Arrow, and Aquaman have been dispatched to deal with the crisis. Hurricane force winds surrounding the device ground Wonder Woman's invisible jet. The hurricane force winds neutralize Wonder Woman and the Green Arrow's ability to attack. Aquaman commands an enormous crustacean to destroy the machine, but the crab is incapable of scaling the pillar the device rests on. Wonder Woman lassoes the pillar. With Wonder Woman and the Green Arrow pulling, and the crab pushing, the three heroes are able to move the device to shore, where it is destroyed. The people of Allomar, however, do not wake.
Crestfallen over their failure, the three heroes return to Earth. Back on Earth, the trio of Justice Leagues hear a radio bulletin, describing the attack of a giant astronaut. Wonder Woman, Aquaman, and the Green Arrow rush out to face the menace, in the hopes of redeeming themselves for their failure on Allomar. A strange machine has paralyzed the entire population of the planet Ullison. J'onn J'onzz, the Manhunter From Mars, the Green Lantern, and the Flash have been dispatched to deal with the crisis. An enormous dragon protects the device. The dragon is able to fashion a defense against each of the heroes individual attacks. Only by working together, as a team, are the Justice League members able to triumph over the dragon, and destroy the device. The populace of Ullison, however, remain paralyzed.
Crestfallen over their failure, the three heroes return to Earth. The giant astronaut pushes a boat out of the harbor. Wonder Woman, Aquaman, and the Green Arrow attack the giant astronaut. A sudden lightning barrage strikes the exact spot the boat was harbored. The Justice League members realize the giant astronaut was actually saving the people on the boat. Wonder Woman, Aquaman, and the Green Arrow attempt to communicate with the giant astronaut, to no avail. The giant astronaut spends the day averting disasters, while the three heroes follow it, from crisis point to crisis point. The Flash, the Green Lantern, and J'onn J'onzz, the Manhunter from Mars, arrive on Earth, just as the giant astronaut is tearing a building from the ground.
The three heroes move in to stop the giant astronaut, only to be thwarted by their teammates. The ground collapses underneath where the building once stood. Wonder Woman explains the situation to her fellow League members. A strange machine has neutralized the gravity on the planet Zomarr, causing the populace to float into the sky. Superman, the Batman , and the Atom are dispatched to deal with the crisis. As they approach the device, it releases spheres burning with extreme heat. Superman pushes forward to destroy the device, but before he can, gravity is restored. Superman realizes that the device on Zomarr is actually causing the crisis on Allamar. When his fellow Justice League members destroyed the device on Ullison, it ended the crisis on Zomarr.
Superman destroys the device. Superman, the Batman, and the Atom apprehend the architect of the triple world crises, Pallkan, before returning to Earth. Superman, the Batman, and the Atom encounter the giant astronaut, in the midst of creating a tidal wave. The Green Lantern prevents them from interfering. The tidal wave generated by the giant astronaut, counters a naturally generated tidal wave. Superman discovers that the giant astronaut is a robot. J'onn J'onzz, the Manhunter from Mars, discovers that the energy the robot has been absorbing, at each of the crisis points, is being broadcast back to the astronaut's spaceship. When Superman and the Martian Manhunter move to board the ship, the robot attacks the Justice League of America.
The robot begins draining away the powers of the Justice League of America. Finding no one onboard the ship, Superman realizes that the ship, itself, is a living being. Superman flies the ship into deep space, until it is too far out of range to send signals to the robot. The ship transforms into an alien creature, to do battle with Superman. The robot ceases to function. Superman hurls the alien on an eternal trip around the universe. The case closed, the Justice League of America place the giant, robot astronaut in their trophy room.