The team is terrorized by a gun-wielding father who is desperate to find his missing daughter. Bunny stirs up accusations of misconduct from Voight's past.

Intelligence investigates a doctor who gave his patients lethal doses of chemotherapy. Roman fights a wrongful shooting investigation.

The crossover starts on Chicago Fire S04E10 The Beating Heart (I) and Chicago Med S01E05 Malignant (II).

When Burgess and Lindsay respond to a call about a stabbing, the assailant turns out to be a kidnapping victim escaping her captor; Ruzek accuses Roman of having feelings for Burgess.

Lindsay and Halstead respond to a shots fired call and discover one survivor: a young girl. Antonio and Olinsky investigate a "self help" group. Platt makes the case to Crowley for why Burgess and Roman should remain partners.

With the suspects still at large and conditions worsening underground, first responders race to reach the trapped victims, while the investigation into the assailants comes into focus.

The crossover starts on Chicago Fire S13E11 In the Trenches (I) and Chicago Med S10E11 In the Trenches (II).