Smallville: Season 4, Episode 6

4 - 6: Transference

Clark hears a painful ringing sound in his ears and is drawn to the prison where Lionel is being held. When he sees Lionel attempt to stab Lex with a strange glowing stone, Clark grabs for the stone causing the two men to switch bodies. Learning his new body has super powers, Lionel immediately begins wreaking havoc on “Smallville”. Trapped behind bars without his powers, Clark must figure out a way to get his body and powers back in order to save his friends and family.