This new series tells the story of a fella called Ash, who is "a talented customs agent with a troubled past". (They always have troubled pasts, don't they?) He is head-hunted to join UNIT - an elite team of law enforcers that operates beyond the jurisdiction of the police. Their mission is to track down hardcore criminals, which Ash is more than happy to do as he has a few scores to settle with certain high-ranking members of the underworld...