Rick Devon is killed outside the public toilet in a park known as a hotspot for drug dealers. From a key that was lost in the toilet, Lupo and Bernard trace Diego Cardenas: a former gang member who's now in charge of a residential home for those with mental disabilities. Cardenas' story of when he was in the park doesn't add up, but he's subsequently killed by gangsters "Big Chuck" and "Momo." The detectives figure out that Cardenas was trying to protect Pete Harris, a resident of the home. Pete was the victim's co-worker and they were working together on the night of the murder.

Pete says that he and Rick walked home after work, and Pete stopped to use the toilet; when he came out, Rick had been killed. Big Chuck and Momo are charged with murder after Pete identifies them as present at the scene, but they insist they only killed Cardenas - not Rick. The detectives discover that Pete is actually Rick's older brother who was given up for adoption because of his disability. Rick had recently traced him, but now all documents relating to the adoption are missing from Rick's files.

The Devons request a reunion with Pete, which becomes tense. Pete's brother mentions that another brother, Ted, said Pete will only drink out of a plastic bottle. Since plastic bottles didn't exist when Pete was adopted in the 1960s, Cutter and Rubirosa realize Ted must have seen Pete more recently. Later, Pete says that when he was in the park toilets, he heard Ted yelling at Rick outside. Ted is charged with murder but this will be difficult to prove because the severely disabled Pete is the only witness. Furthermore, Pete's now moved back in with his family, who may influence his testimony.

On the stand, Pete suddenly changes his story and says ''he'' killed Rick accidentally. The [=DA=]s know this is an obvious lie, but Cutter insists Pete be arrested for murder. He then tells Pete's parents that Pete is likely to be convicted and jailed for life. Mr. Devon refuses to believe this, but Mrs. Devon breaks down with guilt over abandoning Pete. She implicates Ted, and he confesses to killing Rick. Ted tells the court that he didn't want his parents' lives to be disrupted by Pete returning; and takes a manslaughter plea. When the trial ends, Cutter and Rubirosa witness Pete going home with the Devons, who finally seem happy to have him back.

!!!This episode contains examples of:
* AbandonTheDisabled: What happened to Pete as a child.
* BitchInSheepsClothing: Ted seems kind to Pete (whereas another brother outright rejected him), but actually killed Rick in an effort to prevent Pete coming back into the family.
* CainAndAbel: Ted Devon is the Cain, and Rick was the Abel.
* DisabledMeansHelpless: Subverted when Pete reunites with the Devons. They expect him to fit this trope, but he tells them he's doing well in life with a job and a girlfriend.
* DoubleMeaningTitle: Refers both to Pete being mentally "challenged", and the challenges his family has faced with regard to his adoption.
* HalfwayPlotSwitch: The first half is about Cardenas and then the investigation into his death. In the second half, Cutter and Rubirosa try to find out who in the Devon family would have wanted to cover up Pete's adoption.
* HollywoodAutism: One of the residents at the home fits this trope.
* MyGodWhatHaveIDone: Pete's mother has this reaction when told Pete faces a life sentence for Rick's murder.
* TheUnfavorite: Mr. Devon shows very little remorse over putting Pete up for adoption, because the family simply found him too difficult to live with.