Smallville: Season 4, Episode 10

4 - 10: Scare

Lex's secret experiment at Luthorcorp goes awry and causes a dangerous toxin to be released into Smallville. Those infected by the toxin, including Clark, Lana, Lex, and Jason imagine their greatest fears come true and then fall into a coma. Desperate to find a cure, Clark gives some of his blood to Lex and is stunned at what Lex does with the antidote.