Severide lobbies Chief Boden for a favor for Scott Rice, an old friend needing a second chance with the CFD, but Casey and Otis have their doubts. Elsewhere, Mills works to regain his active squad status while Brett and Dawson decide they need a big night out.

Truck and squad are called to the scene of a car crash that has Mills desperately working to save the life of a driver seriously injured in the wreck. Meanwhile, Casey has some doubts about Jack Nesbitt, whose strip club he is remodeling on the side. Elsewhere, Hermann, Otis, Cruz and Chaplain Orlovsky help get their team ready for the peewee hockey championship, but Herrmann might prove more of an obstacle than the other team.

An apartment fire connected to a case of rape and attempted murder resembles an unsolved case in New York, so Sgt. Benson of Special Victims Unit comes to Chicago to help Intelligence with the investigation.

The crossover continues on Chicago P.D. S02E20 The Number of Rats (II) and Law & Order: Special Victims Unit S16E20 Daydream Believer (III).

At Sgt. Voight's urging, a determined Lt. Casey agrees to go undercover in an effort to provide proof of Jack Nesbitt's shady dealings. Meanwhile, Otis and Severide continue to disagree about the integrity of Scott Rice, causing tensions to flare between members of truck and squad. Meanwhile, Herrmann helps out a fellow member of the firehouse.

Lt. Casey puts his life on the line and digs deeper into the shady dealings of Jack Nesbitt. Chief Boden must figure out how to create unity in a divided house, while Severide comes to question his own judgment. A dangerous warehouse blaze quickly gets out of control and threatens members of firehouse 51.

Casey is placed in a dangerous situation while working undercover to bring down a trafficking ring being run out of Nesbitt's club. The squad's high turnover rate results in an unwelcome surprise for Severide. Dawson recognizes that her life is about to change. A new candidate makes an unusual first impression. Residents band together to protest a drug den in their neighborhood.