After the conviction of a child molester, the detectives feel like their work is done. But not before they hear there is an internal investigation going on involving how long the detectives took to finish their investigation. Because of their delay, Dr. Keppler's last victim could have been saved. Stabler defends his investigation. Both Stabler and Benson say they had to delay their case because one of their victims had lied before about being molested in the past.
The SVU continues to take the heat for their case against Dr. Keppler. Munch discovers that the hospital that hired Keppler also knew about his past accusations of child molestation, but hired him anyway. Cragen orders Benson and Stabler to talk to the Denslow Medical Center and see if Keppler and his lawyer have any tricks up their sleeves.
Stabler and Benson speak to the attorney for Denslow Medical Center to further along the investigation on how Keppler can sue the hospital for hiring him, after knowing what he had been accused of in the past. Because of his hiring, Keppler claims he was allowed to molest four more boys who were his patients.
Benson and Stabler pay Keppler a visit and discover him beaten to death, but not before being shot at nine times. Before the body can be examined, they wait for Greylek. Instead, ADA Cabot shows up, surprising everybody. She took the case when Greylek had to take on another case. Benson makes it clear that Cabot had three years to call and check up on her old friends and chose not to.
The detectives now had to piece together who hated Keppler enough to murder him. They narrowed it down Clive Lynwood, whose DNA was found on a glove inside Keppler's home. Stabler and Benson show up with a warrant to search the Lynwood house. They find a gun missing from its box and arrest Clive for murder. Clive lawyers up and doesn't have to say anything more until his court date.
Because the DNA sample was so small, the Judge dismisses Cabot's case against Lynwood and frees him. Cabot feels guilty for losing her case, but Benson assures her they will solve it. Back at the lab, the detectives learn that the killer worked in an environment high in salt, based on the fingerprints found at the murder scene. Benson immediately thinks about Clive's son, Jeff, who works at a fast food restaurant.
Jeff is brought in for interrogation. Benson takes fingerprints off of Jeff's soda cup and runs it to the lab, where they match the prints found on the bullets at the murder scene. Benson returns to the interrogation room and reads Jeff his rights. The mentally challenged teenager says he's fine with talking to the police. When she asks if he knows a Dr. Keppler, Jeff denies it but begins acting fidgety. Jeff later tells the truth, that Keppler molested him when he was younger.
Jeff admits that he went to Keppler's house with his dad's gun. When Keppler lunged at him, Jeff tried shooting him but kept missing. That is when Keppler called Jeff stupid, so Jeff used the gold-plated handgun to hit Keppler over and over again, before finishing him off with a golf club. Cabot witnesses the interrogation and wants Jeff arrested, despite his mental challenges.
Huang interviews Jeff to see if he's mentally ready to stand trial. After Jeff finds out Huang is a doctor, he flips out and attacks him, but Stabler arrives just in time. Huang tells Cabot that Jeff has proven he cannot stand trial because he has the mentality of a child. Cabot disagrees and continues to push the charges.
At trial, Cabot cross-examines Jeff until he breaks and starts yelling at her while chewing at his pencil. The judge interrupts and wants to see both lawyers in his chambers. He chastises Cabot for railroading a mentally challenged teenager, causing her to think about her actions.
Huang encourages Cabot to go with him to interview Jeff's mom. Huang asks if Jeff always had a habit of putting inanimate objects in his mouth, similar to what he did with the pencil. She shows them a collection of Jeff's toy cars that he used to chew on when he was younger. Huang then tells Jeff's parents about a disorder that causes mental slowness when the brain is exposed to too much lead, like in the paint found on toy cars.
Huang shows the Lynwoods and their defense attorney Jeff's latest MRI, which clearly shows that Jeff's brain didn't know how to register control, which would explain his violent lashing out when angry. Huang says that Jeff's mental deterioration could have been prevented if Keppler had diagnosed Jeff when he was young boy.
Back in court, Cabot calls Michael Rowan to the stand, the CEO of the toy company that made the cars Jeff chewed on. Rowan claims that the toy company doesn't use lead-based paint, but Cabot proves him wrong with lab testing and emails. Rowan refuses to answer any more questions and tries to leave. Before he can, Stabler and Benson place him under arrest for reckless endangerment.
The judge is ready to give his verdict to Jeff Lynwood. He finds him not guilty by reasoning of mental defect. The verdict is a huge relief to Jeff's parents. Jeff has to agree to mental evaluation until it's proven he is no longer a threat to himself or others. The Lynwood family receives more good news -- Rowan Industries has agreed to support Jeff financially for life. The detectives were impressed with Cabot's deal and Benson realizes the old Cabot really is back.