After putting out a kitchen fire in an upscale townhouse, Casey, Herrmann, Mouch, Cruz, Otis and Mills find themselves accused of stealing a $50,000 diamond necklace from the home, touching off an internal investigation. Cruz’s brother Leon is caught in the middle of an escalating gang war, leaving Cruz to make a desperate choice to save him. Meanwhile, Dawson invites Casey to her cousin’s fancy Christmas party, and a frustrated Shay has reached her limit with Severide.

From "The Guilt Trip," actor Seth Rogen; Christmas Toys; comic John Witherspoon

From "This Is 40", director Judd Apatow; from "Downton Abbey", actress Joanne Froggatt.

An entire pantry wrapped in aluminum foil tests the chefs. Also: head-to-head battles. Former contestant Stephanie Izard is the guest judge.