S19, E20: Two young engaged scientists die in a fire and a mentally challenged neighbor Charlie Headlind (Guest Star Christian Anderson) is badly burned trying to save the couple. Detectives Cyrus Lupo (Jeremy Sisto) and Kevin Bernard (Anthony Anderson) discover that both of the victims were stabbed before they burned in the fire, leading them to a mentally disturbed woman, Wendy Teal (Guest Star Gretchen Hall), Charlie'’s former girl. Also stars S. Epatha Merkerson, Sam Waterston, Linus Roache and Alana de la Garza.