Season finale. Steve Buscemi guest stars as a patient in witness protection who puts the staff of the ER in danger. Kovac tries to work out his feelings about his marriage with Walter, a patient at the hospice. Moretti returns and tries to apologize to Abby, but she tries to avoid him until he corners her. Sam and Pratt argue over who will accompany the WITSEC patient in the ambulance. Abby and Luka reconcile and decide to leave Chicago for a fresh start.