 Rebecca Ryan has been working as an undercover agent for the Organised Crime Division (OCD) posing as a taxi driver, while investigating London s south-side mob. When she finds her young daughter Lynn brutally murdered she fears her cover has been blown wide open, so she turns renegade and begins a brutal campaign of vengeance against the mob she believes killed her daughter. As she 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. It falls to the world-weary OCD agent Darius Cuise and his newly-assigned, hot-tempered partner Abby Barrett to track down Rebecca and bring her in before all hell breaks loose.