A high-class bachelor party is in full swing in a fancy penthouse apartment. Two police officers arrive at the door responding to a noise complaint. Rather than breaking up the party, the officers wish Will, the groom-to-be, a good night and leave. Meanwhile, Will's friend Clayton Hannigan goes into a bedroom with an escort named Carissa. Moments later, Hannigan and Carissa discover a dead girl lying in the bed.
Benson and Amaro respond to the scene of a potential homicide. But when they arrive at the party, they find the dead girl's body is in the swimming pool. A police officer explains that partygoers claim they don't know her, only that they found her floating in the pool. The detectives learn that most of the partygoers have already fled the scene, except for a few who are stuck on an overloaded elevator. Benson tells officers to hold them for questioning when they get out of the elevator. Up at the penthouse, Benson and Amaro talk to Hannigan, whose clothes are soaking wet; he explains that he got soaked trying to save the unknown victim.
Fin and Rollins arrive on the scene and inform Benson and Amaro that the elevator was full of high-class partygoers including professional athletes, prominent hedge fund managers and secret service agents. Also on the elevator: groom-to-be Will Brady, who happens to be the police commissioner's son.
Benson interviews Will; he tells the detective he has no idea who the girl is. Cragen comes over to make sure Benson doesn't get too hostile; he knows Will could create professional problems for them all if he's not handled right. Cragen tells Will that he appreciates his assistance. Meanwhile, Fin and Amaro grill Hannigan in an attempt to find out who was at the party and where the escorts came from. Nobody seems to have any useful information regarding the dead girl; they all claim not to know her.
At the morgue, Fin and Rollins discover that the victim didn't die from drowning. Instead, the medical examiner found a lethal amount of sedatives in her blood, suggesting that she was drugged. The medical examiner also found semen in her stomach, but nothing to suggest that it wasn't consensual. Fin and Rollins conclude that the girl was a prostitute. The medical examiner tracks the serial number of the victim's silicone breast implants to determine her identity.
The ID comes back on the victim: she's Maggie Murphy, a 16-year-old girl from Winnipeg who ran away from home six months ago. Nobody at the party seems to know who Maggie was or how she got to the party. Cragen sends the detectives back to Hannigan's penthouse to investigate the scene again.
Back at the station, Will shows up with his lawyer and presents Benson and Cragen with a video taken the night of the party. His lawyer explains that the video documents Will's entire evening and proves his innocence.
Fin, Amaro, and Rollins review the eight hours of Will's party video footage, searching for any clues. In the background of one scene, Rollins spots Maggie stumbling into a bedroom. Later, the tape shows Hannigan and Carissa entering the same room. It may not be much, but it's enough to send the detectives after Hannigan.
Cragen advises Benson that they'll need to back off of the case because the suspects are too high profile. He explains that the escorts involved in the case have clients who are high-powered politicians and law enforcement officials; they need to proceed with caution. Benson is annoyed by Cragen's meddling and she wonders if Cragen is hiding something.
Benson and Amaro interrogate Hannigan. He confesses to putting Maggie's body in the pool, reasoning a drowning would create less suspicion. He remains adamant that that he doesn't know who Maggie is or how she got to his penthouse party. Eventually, Hannigan gives the detectives the name and number of his escort, Carissa, to corroborate his story.
Carissa arrives at the station but refuses to talk to the detectives until her lawyer is present. When Benson leaves, Carissa begins flirting with Amaro. Cragen interrupts and tells Amaro to be careful. After her lawyer arrives, Carissa tells Benson and Amaro that she works for an escort service and that she knew all the girls at the party except Maggie. The detectives decide to talk to Carissa's booker, Bart Ganzel.
When Rollins and Amaro arrive at Bart Ganzel's residence, they discover a party in full swing, with attractive escorts everywhere. Detective Brian Cassidy, formerly of the SVU, is now working as Bart's bodyguard. He gets a tipoff about the detectives' arrival and tells Bart that they need to leave immediately. Rollins and Amaro intercept them on the way out and Cassidy gets into beef with Amaro. It comes to blows and Cassidy and Bart are immediately arrested.
In the interrogation room, Benson explains to Amaro that Cassidy used to be a detective. Cassidy explains that he's been working undercover for the past three years. When questioned about Maggie, Cassidy says she's not one of Bart's girls. He encourages Benson and Amaro to question Bart, saying he's got every reason to cooperate. Cassidy also explains that the detectives need to hold him, so as not to blow his cover. Benson makes a show of locking him up.
Rollins and Fin question Bart Ganzel, who re-affirms that Maggie isn't one of his escorts and she didn't arrive with any of his girls. According to Bart, the only escort he hasn't heard from is Anya, a Colombian escort who flew back home the day after the murder. The detectives search Anya's apartment and find an empty pill bottle that matches the drug Maggie was poisoned with. The detectives decide to question Cassidy about Anya.
Benson and Amaro meet Cassidy in a bar; Carissa joins them shortly after. When asked about Anya, Cassidy tells Benson that Anya used to work for another escort booker, Delia, who is Bart Ganzel's main competition. Cassidy warns Benson that if she's going after Delia, she needs to be careful: Delia has rich and powerful clients to protect her. Meanwhile, Carissa continues trying to seduce Amaro.
Benson and Amaro visit Delia at her farm to question her about her connection to Anya and Bart Ganzel. Delia is feeding a baby goat when the detectives arrive, and she certainly doesn't seem like a notorious madam. When asked about her escort service, Delia describes it as a "match-making service", and though she says she's heard of Bart Ganzel, she doesn't know him personally. Back at the station, Cragen urges Benson to back off of the case - he's being blackmailed.
Benson and Cragen are interrupted by a call: the former governor has been found dead in his home. The detectives soon learn that the governor was with one of Delia's escorts at the time of his death. During the autopsy, the medical examiner discovers a drug in the governor's system; it's the same drug they found in Maggie's system. The detectives suspect that Bart Ganzel is attempting to frame Delia. They're caught in the middle of a war between two powerful escort service kingpins.
Fin and Rollins track down the escort who was assigned to the governor; she tells them he was dead when she arrived. She says she called her booker, Iris, who told her to leave the scene of the crime immediately. The detectives call in Iris; she too denies knowing anything about drugs in the governor's body. Iris goes on to tell Benson and Amaro everything they need to know about Delia: that she's a notorious madam and that she's waging a war against Bart Ganzel. She claims that Delia sent Maggie to Hannigan's party and had another escort drug her in order to destroy Bart's business. The detectives head back to Delia's farm to place her under arrest.
Later that evening as Amaro is leaving the station, Carissa catches him in the parking lot. She tells him she's afraid for her life. Amaro wants to take her into the station house, but Carissa insists she has to leave.
In court, Delia is arraigned. Her bail is set at $2 million, which her lawyer pays immediately. Delia's lawyer then warns the detectives that Delia has influence over extremely powerful people, and that they should leave her alone.
At home, Cragen wakes up in the middle of the night to find Carissa in his bed with her throat slit. It's a mystery that will have to wait until Season 14 to be solved.