A member of the Firehouse family clings to life and members of the Chicago Med staff discover a highly unusual parallel between cases - a three-part story arc crosses over into "Chicago Fire" and concludes the following night on "Chicago P.D. Following a knife attack, a member of the team lies in peril and their condition takes a sudden turn for the worse, leaving Dr. Connor Rhodes (Colin Donnell) and Dr. Toni Zanetti (guest star Julie Berman) scrambling to race against the clock. Word quickly spreads that some of Connor's fellow doctors feel he should have operated sooner, causing tension at the hospital. Dr. Natalie Manning (Torrey DeVitto) makes preparations for her pregnancy and Nurse April Sexton's (Yaya DaCosta) brother (guest star Roland Buck III) struggles through his first day at the hospital. Meanwhile, members of the Chicago P.D. Intelligence Unit help investigate whether the case of a women clinging to life after Firehouse 51 pulled her out of a burning building is attempted suicide or murder. As the investigation deepens, a surprising parallel to other patients surfaces.