S4, E22: Clark discovers the reason he was sent to Earth after a nightmare foretells a horrible event that's about to befall Smallville, and he visits the cave to seek answers from Jor-El. His biological father tells Clark he must reunite the three crystals immediately or an enormous disaster will devastate the planet that even Clark won't be able to stop or survive. Meanwhile, after finding Lana with Genevieve Teague's dead body, Lex helps the teen escape Smallville then takes shocking action to get one of the crystals away from Lionel. Realizing the elements are connected to Clark, Chloe tries to stop Lex from discovering the truth.