The brutal rape and subsequent death of a female motorist turns out to be an informant for the FBI acting as a cyber vigilante for catching on-line pedophiles to capture the predators. Stabler, along with the homicide detective who found the victim's husband murdered, follow the trail of evidence for the latest victim she had been tracking, leading them to the US Attorney's Office and a trip to Prague for Stabler to assist the Czech authorities when they find the kidnapped girl.