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.

Ryan has spent years putting his brutal past behind him. A different man now to the stone cold killer he was a lifetime ago. But when an old face from the past arrives on his doorstep, Ryan is called upon to repay a blood debt from years ago. But the price is too high. Betrayed, and with his life falling apart around him, Ryan goes on a murderous, bloody revenge spree against the Ten Men who took his life away from him. Ten men took away his life. Now Ten Men Will Pay.