A sassy new operative arrives at the unit just as the group go undercover to entrap a group of young thieves. But a mistake leads to a kidnapping, placing everyone in danger.
When a homicide investigation into the disappearance of a teenager babysitter fails to reveal any useful evidence, Church and Angie go undercover to infiltrate a sinister criminal family.
Working with criminal profiler Vicki Quinlan and the new Head of Homicide Frank Callahan, the Undercover Unit investigate a serial murderer but their attempts to trap the killer leaves Mackenzie fighting for her and her best friend's life.