Smallville: Season 4, Episode 16

4 - 16: Lucy

Lois' younger sister, Lucy, with whom Lois doesn't get along, comes to town and charms everyone she meets. However, Clark discovers a darker side to Lucy after he catches her stealing money from a bar and forces her to reveal the truth about her sudden appearance in Smallville - a truth that puts Lois in grave danger. Meanwhile, the crystal disappears from Lana's apartment and Jason accuses Lionel of stealing it. Lois' sister, Lucy, appears in this episode.