Lieutenant Casey deals with the fallout of his sister Christie's impending divorce. Meanwhile, Dawson and Mills settle into their new roles at Station 51. Elsewhere, Brett can't decide if she wants to leave Chicago and the Molly's crew still can't figure out how to get the food truck started.

Members of Firehouse 51 are forced to contend with a house fire, but when the injured owner is rescued from his cellar clutching a suspicious box, Lt. Severide brings in Sergeant Voight and Detective Lindsay into the mix for further investigating. Elsewhere, Mills wonders if the dangers of Newhouses's off-duty gig are worth the cash returns, while Molly's II is in dire need of a good chef.