Lois's younger sister, Lucy, arrives in town, and Clark learns that she has a shady past when he catches her stealing money from the Talon's register. Also, the ancient stone is taken from Lana's apartment, and Jason suspects Lionel.

On the night before the prom, a popular student crashes her car into a kryptonite-filled ravine and her spirit ends up taking over other people's bodies. Elsewhere, the body of Dr. Swann's assistant, Bridgette Crosby, is found in a shallow grave on Lex's property, and Jason accuses Lex of killing her. Lifehouse performs at the dance.