TheseriesisaboutaCustomsOfficer,MarcusAshton(Ash)whoisrecruitedtoanewlawenforcementteamtaskedwithhuntingdownsomeofBritain'smostwantedcriminals.TheseriesisinspiredbythebookofthesamenamewhichdetailsthecareerofformercustomsagentCameronAddicott,writtenbyKrisHollington.