Superman stopped a gang of hijackers with a molecule gun attempting to rip off an 18-wheeler on his way home to Smallville. Clark had dinner with his parents and heard a pulsating sound coming from the moon. He changed clothes and left earth for the first time. On the moon, Superman found a crashed spacecraft and a dying alien. The alien told him of a warring race called the H'tros. The alien died after telling him the H'tros were going to attack his planet. Superman activated the return device on the ship and sped off to the alien's world.
On the alien world, Superman leaned more about the attackers - they were mechanical and seemed to exist only to destroy organic life. Superman was able to stop the invasion on his own. The aliens, mourning for the deaths, sent Superman home.
Perry White announced to his crew that NASA had picked up a signal coming toward Earth. Clark knew it to be the H'tros. He changed and headed toward the invaders. Inside one of the ships, he found the being who'd created the mechanical army. After defeating the H'tros, Metropolis held a parade in Superman's honor.
Clark had dinner with his parents again, still trying to understand people - one race barely thanked him for saving them, another honored him.