Twenty years after being convicted of the rape of a teenage girl, Ray Schenkel is released, much to the dismay of retired detective William Dorsey. When a teenage girl is raped on the route Schenkel would have taken home, Stabler goes undercover as a recently paroled sex offender so that he can get into the same therapy group as Schenkel, and the same halfway house. Cragen worries that Stabler may be getting in over his head.

The team investigates when young Carly Hunter disappears while walking home from school one day. While processing evidence found at the scene, Warner realises that the little girl has leukemia, and they need to get her home as soon as possible to begin treatment. Despite the ransom drop going wrong, the detectives are able to find the little girl thanks to evidence O'Halloran finds at the scene, but as she tells her story to Stabler and her mother, it soon becomes clear that her kidnapper is someone very close to home. Stabler and Warner end up becoming hostages when the kidnapper approaches Jake Hunter directly.

The mother of a kidnapped young girl points the detectives towards her father, an ex-con, but it is soon discovered that the grandfather is a master thief and has many enemies. However, because of Alzheimer's, the grandfather can't remember much of his past.