Prisoners -- How far would you go to protect your child? Keller Dover is facing every parent's worst nightmare. His six-year-old daughter, Anna, is missing, together with her young friend, Joy, and as minutes turn to hours, panic sets in. The only lead is a dilapidated RV that had earlier been parked on their street. Heading the investigation, Detective Loki arrests its driver, Alex Jones, but a lack of evidence forces the only suspect's release. Knowing his child's life is at stake, the frantic Dover decides he has no choice but to take matters into his own hands. The desperate father will do whatever it takes to find the girls, but in doing so, he may lose himself, begging the question: When do you cross the line between seeking justice and becoming a vigilante?