It's been four months since Benson began fostering Noah, the Baby Boy Doe whose sex worker mother, Ellie Porter, was brutally gang-raped and murdered in the Season 15 finale. Despite the tragic circumstances, Benson is enjoying motherhood immensely and her love for the boy further motivates her to find Ellie's killer.
After last season's fight that nearly cost him his shield, Amaro has been relegated to traffic duty with a new partner, rookie Officer D'Bora Maresko. The pair busts a john getting serviced by an underage girl named Luna Garcia. While being questioned, Garcia smacks Maresko and flees in terror, yelling "He'll friggin' kill me!" When Amaro catches up with her and tries to discern whom the "he" is, an SUV with a QuikRide car service logo on the window drives by and a woman glares at them from the back seat.
Back at the precinct, the team learns that not only is Luna underage, she's a material witness in the rape-homicide of Ellie Porter. As Fin and Rollins walk Luna to the car to take her to SVU, gunshots ring out and a car window shatters! Fin returns fire, and in the commotion, the shooter, Diego Ramirez, runs into the street and is clipped by a passing car. He rolls off the hood to find Fin with a gun to his temple.
At SVU, the squad meets their newest member, Detective Dominick "Sonny" Carisi Jr., a boyish-looking loudmouth from Staten Island sent to fill in for Amaro. He wants to take a run at Luna, but Benson puts him in his place. Luna claims she doesn't know Ellie, but after Carisi bluffs that he can pull some strings to get her T nonimmigration status to protect her from her pimp, she gives up the address of the house she worked out of. The plan is to stake out the house and send in an undercover to infiltrate the ring. They go with someone with a known gripe against the NYPD... Amaro.
While watching the house, Amaro pulls over Joaquin Esteban for running a red light, promising he'll forget the ticket if Joaquin gives him info on the ring. Joaquin is suspicious, so Amaro proves himself by warning him that the house will be raided that night.
That night, SVU busts the house and finds a number of illegal Mexican girls, as well as Mariana, a 14-year-old Ukrainian girl. They also find Joaquin, whom Fin lets walk after he name drops Amaro. Joaquin immediately calls up Amaro, thanks him for the favor and puts him on retainer. The setup worked.
The problem is, Mariana refuses to talk. Rollins notices her cell background photo is of an infant and tells Mariana that they raided a house back in May and found kids inside. She asks her where her baby is. TARU also goes through the trafficked girls' phones and finds they all have the QuikRide app.
At the QuikRide offices, Fin and Rollins meet with owner Angel Perez, who admits the company has had problems in the past with drivers shuttling around working girls, whose rides were paid for by an offshore shell corporation. Five months earlier he had to close the account of Tino Aguilar, aka Little Tino, the pimp Ellie worked for, for being rough with young girls in the cars.
Turns out the girls in Tino's house also used QuikRide, paid for by a similar shell corporation. Benson heads to Attica to meet with ADA Barba and Little Tino to confirm her theory that Tino and Joaquin share the same boss. Tino is afraid to talk, and when Benson presses him again about Ellie's murder, Tino says she shouldn't be so worried, considering she got a baby out of it. He threatens Noah's safety and hints that there are dirty cops working against her.
Speaking of Amaro, he meets up with Joaquin again to collect his payment and to inform Joaquin that Benson and the DA are leaning on Little Tino. Joaquin better start talking if he doesn't want to be left out in the cold. But it looks like Joaquin does more than that...
In Attica, Little Tino gets shivved by three inmates and ends up in surgery, lucky to be alive. In the Bellevue prison ward, an orderly plunges a syringe into Diego's neck, killing him. In a car in Queens, Mariana and a john are found shot to death. Benson calls Lucy, Noah's nanny, to tell her to stay inside, only to find she's at the DeWitt Clinton Playground with Noah. Suddenly Benson hears shots fired over the phone. She races to the playground to check on Noah's safety, and luckily no one was hurt.
Amaro confronts Joaquin, who denies any involvement. Just then Rollins and Fin burst on the scene and arrest both men. Joaquin maintains dirty cop Amaro set him up.
Meanwhile, Benson and Carisi head back to the QuikRide offices, only to find they have been ransacked. Angel yells at them to leave, saying the vandalism occurred because he talked to the other detectives.
Benson and Fin go to the Attica hospital ward to speak with a now-conscious Tino, but are intercepted by his mother, Almina Aguilar. Benson demands to know who ordered Ellie's killing, and Almina reluctantly admits that while she doesn't know who Tino's boss is, she does know his bottom, Selena, who breaks in the new girls. She tells them to book a date with a girl named Carmen on Craigslist to find Selena.
At a seedy hotel, Carisi poses as a john and waits for Carmen to arrive. He gets aggressive with her and she runs to the bathroom to call Selena. Moments later, Selena and her driver arrive and put a gun to Carisi's head, but Benson, Fin and Rollins take them down.
In the interrogation room Selena refuses to talk, and her lawyer claims she's just as much of a victim as the other girls and was trafficked herself. But Benson doesn't see her as a victim; to her, she's the woman who put her son's life in danger.
The detectives meet with Luna again, who admits she and Selena are from the same village in Mexico, where girls are frequently kidnapped and forced into prostitution. Back in Vargas, everyone knows Selena - she was one of the first girls taken to Tenancingo, Mexico, the epicenter of narco sex trafficking.
Turns out the Federal Task Force is already onto Tenancingo, a poor village made up of shacks except for a few gated mansions where the traffickers rape the kidnapped girls, get them pregnant, and keep the babies as hostages. Barba shows the team passport photos of the men believed to own the mansions, one of whom is Teodoro Juarez. The team recognizes him as Angel Perez, and realizes he staged the QuikRide office vandalizing.
With the trafficked women still refusing to talk, Benson realizes the way in is through their children back in Tenancingo. They'll give up everything to save their babies, just like Benson would. She and Rollins show Selena a photo of her son Miguel, who is living in Angel's Mexican mansion, and she agrees to cooperate, divulging details about Angel's organization.
Armed with signed statements from Little Tino, Joaquin, six trafficked girls and Selena, the squad goes to pick up Angel at his Staten Island home. When they try to arrest Angel, he threatens Noah, elbows Fin and pulls a gun on Benson... until Fin shoots him dead.
Outside the gates of Rikers, Selena is released and reunited with her son Miguel. Benson watches, moved. She later goes home to Noah, cradles him in her arms and whispers to him that his mother's killer will never hurt anyone again.