S4, E3: When Platt (Amy Morton) goes to her father Robert's (guest star Chelcie Ross) house for dinner, she warns him to be careful with his new girlfriend Natalie (guest star Lilia Vassileva). Following dinner, Platt is physically assaulted as she's getting into her car and is rushed to Chicago Med. Voight (Jason Beghe), Lindsay (Sophia Bush) and Halstead (Jesse Lee Soffer) arrive at the hospital to investigate, and a concerned Mouch (guest star Christian Stolte) finds himself being questioned. Meanwhile, Antonio (Jon Seda) leads the rest of Intelligence at the scene as they look into previous threats against Platt, but his attention shifts when he is called into Robert's townhouse and finds signs of an even more gruesome attack on Platt's father.