In this episode Clark discovers Kryptonite for the first time.
Lois and Clark investigate a suspicious EPA story in Smallville. But it isn't man-made toxins the feds are after - but a chunk of Kryptonite, the substance that can rob Superman of his powers or even his life.
Wayne Irig, a neighbour of the Kents, finds a piece of a meteorite and sends a sample to the laboratory for examination. A week later, a government agency takes over his farm saying that they have to investigate about environmental violations. Wayne knows that they are looking for the meteorite and he gives it to Martha and Jonathan to hide it. Perry sends Lois and Clark to Smallville to investigate this EPA report.
Jonathan shows Clark the meteorite and they find out that it affects Clark and makes him weak. While investigating, Lois and Clark realise that Wayne has disappeared and they know that something is wrong. They get caught only to find out that Jason Trask is behind everything and is looking for the meteorite to kill Superman.
Trask kidnaps Clark's parents and threatens to kill them if Clark will not tell him where Superman is. Clark admits that he is Superman but since he does not have his powers, Trask does not believe him. Clark gets his powers back and saves his parents. Trask sees it and he uses the meteorite to kill him but Clark manages to destroy it. The two of them fight and Trask gets killed by Sheriff Rachel Harris. Lois writes the story and together with Clark names the meteorite Kryptonite.