A member of Firehouse 51 clings to life and takes a sudden turn for the worse as medical staffers race to give treatment. Meanwhile, Dr. Natalie Manning prepares for her pregnancy and members of Chicago P.D. probe the case of a woman pulled from a fire.The crossover starts on Chicago Fire S04E10 The Beating Heart (I). It continues on Chicago P.D. S03E10 Now I'm God (III).