“Book 27″ (season 1, episode 13)

Season one finale “Book 27” is action-packed: Leland and Sheryl get engaged, and Kristen subsequently informs her mother she can’t see her grandkids ever again. Then, Kristen discovers that RSM Fertility—the clinic that helped her conceive her daughter Lexis—is in league with “the 60” and may be deliberately trying to create morally corruptible children. Finally, LeRoux walks free after having his conviction reversed (thanks to Leland, of course), and promptly starts threatening Kristen and her daughters. She does what she thinks she must, and brutally murders him before he can do any more harm.
Though law enforcement doesn’t suspect her, the act does not go unnoticed: when she gets home, she picks up a rosary and it sears a cross-shaped burn into her hand.