During a heatwave, Wysocki and Evers investigate a homicide where the son actually saw his father's murder. In the meantime, Colvin gets a new driver. And Gibbons reaches out to Liam to help him with his constituents.

After five people are shot in Lincoln Park, the mayor blames Colvin for her lack of police work. Colvin puts Wysocki and Evers on the case to put her image to the public in a better light. Also, Isaac and Vonda are asked to look into an old domestic-abuse case.

While Teresa and Jarek set the stage for their case against Alderman Gibbons, their effort to clean up Chicago takes an unexpected turn when a deadlocked jury acquits a corrupt city official. Suspicious, the two mount an investigation, only to discover that jury tampering is just the tip of the iceberg.

The case against Alderman Gibbons escalates when Colvin, Wysocki and Evers scramble to locate a star witness. Meanwhile, as Liam rushes to collect more evidence, he is forced to take matters into his own hands.

FBI Special Agent Cuyler returns to see Superintendent Colvin; Jarek deals with family issues that have haunted him for years; and the case against Alderman Gibbons comes to a conclusion.