At the site of a train accident, Peter Mills (Charlie Barnett) becomes deeply upset when he observes the dead body of a young victim. Unable to shake his emotional distress about the event, he questions his future as a firefighter. Dawson (Monica Raymund) and Shay (Lauren German) save a 6-year-old girl whose mother (guest star Kat McDonnell) is abusing her -- but their confrontation leads the woman to resort to dire actions. Meanwhile, Severide (Taylor Kinney) aggravates his injury while rescuing a heart attack victim and Shay sends Clarice (guest star Sheri Appleby), her married, pregnant ex-girlfriend, back home to her husband. Jesse Spencer, David Eigenberg and Eamonn Walker also star.