Law & Order: Special Victims Unit: Season 8, Episode 6

Infiltrated

Casey Novak is forced to get Benson, still undercover with the FBI, to come back to New York to testify in a rape case. While undercover with an Oregon environmental group, Benson is injured by an overzealous deputy sheriff and charged with assault. She is eventually released but is questioned about her group's involvement with a murder. She then sets out to clear her group's name and finds that the murdered man was a pedophile. She finds a room under his garage and discovers the murder scene. The local sheriff finds two sets of prints at the scene, the murdered man's and those of a ten year old girl who went missing seven years ago. Benson is then released from the FBI (it turns out that the group she had infiltrated had nothing to do with terrorism; the actual terrorist leader had been arrested two days ago) to go back to New York. As she is still unaware of the urgency of Novak's case, she decides to stay and help the FBI find the missing girl. In the end Benson finds the girl, who had developed Stockholm syndrome. Benson just makes it back to New York in time to testify.