Rebecca Ryan (Claire Goose) has been working undercover for the Organised Crime Division (OCD), posing as a taxi driver while investigating London's south side mob. When she finds that her own young daughter has been brutally murdered she fears that her cover may have been blown. As Rebecca trawls the seedy depths of London's underworld, hunting down her daughter's killers, the lines between good and evil, right and wrong, begin to blur as do her notions of justice and revenge. She embarks on a brutal, bloody campaign of vengeance against the gang she believes is responsible. The fragile bonds that hold the gang together begin to unravel and death pervades. No one is safe, including the elusive and mysterious Jade (Sarah Harding). A trail of blood begins to flow from Rebecca's quest for justice and it's left up to the world-weary OCD agent Darius Cruise (Anthony Ofoegbu) to bring her in. He and his newly assigned, hot-tempered partner Abby Barrett (Donna Air) must do what no cop likes to do - to go after one of their own and, if necessary, take her down.