(1st Appearance of Mon-El)
"Superboy's Big Brother" - - *One evening outside Smallville, Superboy rescues an older teenager from an exploding rocketship. Although the boy cannot remember his origin, his super-powers, a medallion, and a note written by Superboy's father Jor-El convince them both that he is Superboy's older brother. Christened "Mon-El" after the day he arrived (Monday), he is adopted by the Kents, and takes the secret identity of Bob Cobb, brush salesman.
One night, Superboy notices that Mon-El's belt buckle is made of non-Kryptonian metal. Playing a hunch, he exposes a sleeping Mon-El to Kryptonite and determines that, whoever this stranger is, he is not from Krypton. When the two of them confront a gang of criminals who are catapulting lead boulders on Smallville, Mon-el collapses, the crooks escape, and Superboy is convinced that his new friend is in league with them.
Intent on exposing this ruse, he confiscates the lead boulders and paints them to look like Green Kryptonite, and then arranges a fake meteor shower. Feigning agony, he watches Mon-El weaken; then he stands, accuses him of lying, and shows him the "evidence." However, the exposure to lead has returned Mon-El's memory, and he explains that he is a traveller from a Krypton-like world, Daxam, who landed on Krypton and met Jor-El and Lara shortly before the planet exploded. Moreover, he says, a Daxamite is doomed once exposed to lead.
Fortunately, Superboy is able to save Mon-El's life by projecting him into the Phantom Zone, and vows someday to find a way to free him. *Source: The Official Legion of Super-Heroes Index #1 - Published by ICG.
Also contains the back-up story: "The Super-Cop of Smallville".