The Intelligence Unit finds the naked body of Grace Johnson on a football field. Her sister tells Atwater that Grace had a double life as part of "lingerie parties" run by a man named Vincent. Vincent directs the team to Grace's ex Ricky, who disappeared after learning of Grace's death.
But Burgess uncovers a pattern that suggests a serial killer. She interviews a woman who was visibly upset at the scene and discovers that the woman has found Grace's death is just one of thirteen. While Ricky is arrested the team is able to find the only surviving victim, Sienna Brody, who identifies Ricky's father as her rapist.
Based on a tip from Ricky the cops find Franklin just as he's burning the last of his evidence and put him behind bars, even as they wonder how many other missing yet to be located girls might be other victims.
Meanwhile, Lindsay finally comes face to face with her father as Halstead looks into Jimmy's past. The two of them have dinner with Jimmy and Lindsay's mother, but Lindsay declines Halstead's request to run her father's DNA as well. And Burgess deals with Ruzek leaving for a deep cover assignment and meeting his replacement, Kenny Rixton.