Law & Order: SVU Season 20 Episode 20 revolves around a pregnant thirteen-year-old named Mackenzie. After Mackenzie has a loud argument with her stepdad, the neighbors call the cops. Garett insists it's no big deal even though his arm was cut in the fight, but the two are taken to a hospital and SVU is called in after Mackenzie tells the doctor at the hospital that she is pregnant.

Mackenzie refuses to tell SVU who the father of her baby is. The team investigates and finds Mackenzie had a secret Instagram account with photos of her kissing two boys. She goes to a Catholic middle school where the priest in charge doubts anyone is having sex. He IDs the two boys nevertheless, who deny doing anything to Mackenzie and suggest a teacher was raping her.

The cops talk to the teacher, who denies it. He offers a DNA sample and suddenly Garrett does not want the cops to investigate further.

Benson wants to go to court to get an order for a paternity test. Rollins passionately disagrees. She thinks the girl has a right to privacy, and what if one of the other kids is the father? Mackenzie interrupts. She told Garett that Mr. Dreyfus raped her and he went off all angry.

Benson and Rollins rush to Dreyfus' house where he is found dead with Garett sitting on the couch. Garett is arrested. Soon, Dreyfus' fiance comes to see Stone and says Dreyfus was gay but not out at school and the two were going to marry.

Benson confronts Mackenzie who says she's not scared of Garett and wants to go home.

At trial, Stone plans to call Mackenzie as a witness against Garett but it turns out she and Garett are married. Apparently in Missouri it is legal for a child her age to marry with parental consent.

Stone and Benson try to get the marriage annulled but the judge won't do it, and Garett's attorney gets the criminal court judge to agree that all references to the marriage are out. But then Benson comes up with a last-ditch effort to protect Mackenzie and nail Garett for the murder.

To find out what happens, watch Law & Order: SVU Season 20 Episode 20 online.