Kim Delaney begins a short-term return as Det. Diane Russell to help the precinct track a serial rapist, but her own private demons turn the reunion into one hell of a drama for Andy and company. Meanwhile, Jones struggles to balance work with his new friendship with a troubled teen (Andre Jamal Kinney); a pair of high-schoolers have something to hide about a possible arson; and Clark puts his foot down with Devlin after she tries to spice up their love life. Peter Carlin: Michael Reilly Burke. Devlin: Chandra West. Kurt: Billy Kay. Nancy: Molly Hagan.