In the SVU bullpen, the detectives are heading out for a night off while Amaro and Munch man the SVU unit. Shortly after the other detectives leave, a young woman enters the station and tells Amaro that she was raped by Brian Cassidy, who just happens to be preparing to testify against his old employer, Bart Ganzel. Munch suspects that Ganzel is attempting to sabotage Cassidy's testimony before the trial, but they'll have to look into the accusation.
Munch and Amaro head to Cassidy's apartment to investigate. While speaking to Cassidy at the door, Benson appears dressed in pajamas. Amaro and Munch quickly put the pieces together: Benson has been secretly seeing Cassidy. The next day, the detectives give Cassidy the run down on the victim's accusations. Cassidy recognizes the woman as a former working girl, but he claims that she's lying about the rape charge.
Back in the bullpen, the detectives agree to help Cassidy in any way they can, before Internal Affairs finds a way to put Cassidy under for good. Fin and Rollins head out to interview the alleged victim, Heather. They quickly discover that Heather's boyfriend has been visiting Ganzel in prison. It's looking more like a setup every second, but Barba advises that they'll need solid evidence of a conspiracy.
On the witness stand, Heather delivers a moving testimony, sticking by her claim that Cassidy raped her. Cassidy's defense presents a good case, but Cassidy is concerned about Amaro's testimony. On the witness stand, Amaro tries his best to avoid throwing Cassidy under the bus, but the prosecutor proves tricky. Barba begins to suspect that Cassidy's lawyer, Kerns, is working against Cassidy.
While cross-examining Amaro, Kerns brings a surprise witness into the courtroom: a woman that Amaro was involved with during his undercover operation years ago. Amaro had a relationship with Cynthia during his undercover days, until he was able to convict Cynthia's brother of dealing drugs. Now, Cynthia wants nothing to do with Amaro, who is upset at Cassidy for digging up his past.
Kerns tries to convince Cassidy to plead guilty to the rape charge to avoid a lengthy trial, but Cassidy refuses. Meanwhile, Munch tells Amaro that Cynthia is suing him for child support. Amaro tries to track down Cynthia to discuss the suit (and the child he just found out about), but Cynthia doesn't want to speak to him. Amaro discovers that Cynthia's new boyfriend is using her son to traffic drugs.
Back at the station, Munch tells Amaro that he needs to tell Maria about Cynthia and her son. Amaro calls Maria to break the news about his son. The next day, Amaro ambushes Cynthia in her lawyer's office and runs into his son. Amaro is not here to talk about the lawsuit, though. He's upset with Cynthia because her boyfriend is using her son to traffic drugs. He begs Cynthia to protect their son.
Amaro and Cassidy decide to cooperate in order to save each other. Cassidy and Rollins go undercover to infiltrate the drug ring that Cynthia's boyfriend is working for, and with a little cunning, the squad is able to nail Cynthia's boyfriend and Heather's boss in the same bust. Eventually, Heather confesses to Benson that she made the rape story up. The next day, the charges against Cassidy are dropped, and Amaro begins to build a relationship with Cynthia and his newly discovered son.