Trying to prove Mon-El isn't actually Kryptonian, Superboy accidentally exposes him to lead, which both poisons him and returns his memory. Mon-El remembers that he is a space explorer from Daxam, who visited Krypton, meeting Jor-El and Lara, before arriving on Earth. To save his life, Superboy sends Mon-El into the Phantom Zone until he can cure him of his lead poisoning.; When a space ship crashes outside Smallville, Superboy finds an amnesiac, super-powered youth who might be his older brother. He christens him Mon-El and sets him up with a secret identity, but he soon finds evidence that Mon-El is not, in fact, Kryptonian.; The entire Smallville police force is quarantined so Superboy has to take their place.