Law & Order: Special Victims Unit (1999) : 7x13

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.