A murder investigation becomes personal for Voight when his son Justin is attacked in the same manner as a widowed, single mother whose body is found in the trunk of her car.
When Upton and Ruzek answer an emergency call to an abandoned house, their investigation leads them down a dark path. Upton feels the pressure of the secret she and Voight are sharing.
Halstead and Atwater go undercover to prevent military-grade weapons from hitting the street. Meanwhile, Voight calls in a favor as a last-ditch effort to clear Olinsky's name for Bingham's murder.