Olinsky goes under cover as a hit man for hire after Lindsay is tipped off about a grieving father looking to avenge his daughter's death; when Ruzek returns from his undercover assignment, Voight puts him on patrol duty.
When the crushed body of a young teen who ran away from a treatment center for troubled girls is found in an abandoned building, Voight sends Halstead under cover as a guard to investigate the center from the inside.
The investigation into the murder of a sex offender leads to a private police force operating independently of the Chicago PD; Halstead checks Jimmy's DNA to find out if he really is Lindsay's father.
Evidence from the case of a young woman who was shot to death confirms the Chicago P.D. has a serial killer on its hands; Voight welcomes Kenny Rixton to the team when Ruzek takes another assignment.
A priest and parishioners block law enforcement from entering a church where two murder suspects are suspected of hiding; Rixton is caught in a lie with Voight.
