Chicago Police homicide detectives Jim Ryan and his partner Brian Dwyer, already loaded with open homicide investigations, are assigned to investigate a robbery homicide at a currency exchange on Chicago's south side. During the robbery the manager of the currency exchange is shot and left for dead, and an armored car messenger making a money delivery is murdered. The investigation quickly expands to a second crime scene when the manager's husband is found murdered and their home torched.

The investigation takes an unexpected twist when neighbors say they saw the manager leave the home earlier in the morning with two men that appeared to be detectives. Their suspicions are reinforced when a witness gives Dwyer the license number of the getaway car and it is registered to a Chicago Police Department unmarked squad car assigned to the 5th District Tactical Unit. When evidence technicians processing the car find the currency exchange manager's fingerprints in the back seat of the car, the two tactical unit officers assigned to the car become prime suspects. At the same time, Ryan and Dwyer themselves become suspects when the FBI begins investigating a mob murder.

Ryan and Dwyer continue to pursue leads in the currency exchange investigation and identify the actual offenders. An informant leads them to a suburban storage rental business where the offenders are planning their next score. When the suspects are cornered, it turns into a deadly gun battle for both the police and the suspects. One suspect is killed and Dwyer is shot.