Sherlock consults on the case of a serial killer nicknamed 'The Balloon Man,' a child abductor who has murdered eight victims since 2005. Sherlock's signature bluntness doesn't endear him to the family of the killer's latest target, but he manages to get a lead that helps him identify the Balloon Man's van as a decommissioned police vehicle. The cops quickly track down the van and are shocked to find that it is being driven by 19-year-old Adam Kemper--the Balloon Man's first victim. With time running out, Sherlock realizes that Kemper is the only person who can lead them to the killer and save the life of the abducted child.