Larisa Polonsky

Lt Severide is targeted by an arsonist, Battalion Chief Boden clashes with Gail McLeod on the anniversary of Andy's death, Shay has suspicions, and Mari visits Mouch.

Severide wants to implicate the serial arsonist, Dawson and Shay face the unexpected on a routine call, suspicions indicate Clarke is the mole, and Mouch campaigns for union president.

The shooting of a child in their neighbourhood forces Cruz and his brother to think about the gang, Isabella gets Mills to dress up for a gala, Casey feels sad he will be seeing Dawson less, and Shay gets in deeper with Devon.

Severide tries to prove his suspicions about the arsonist's identity, Casey gets accustomed to his new lifestyle, and Dawson goes on a date with a regular from the bar.

Boden tries to keep the firehouse from closing, the romance between Dawson and Casey grows, Cruz worries about his brother's safety, and Severide and Katie make up for lost time.

Severide is on edge after the arson attack, fearing what might be in store next. Shay and Dawson, meanwhile, plan to party away their problems.