Charlotte Granger is the head of a new branch of MI5 called the Police Protection and Assistance Unit. When assigned to the Serious and Serial branch of the Metropolitan Police, she expects action, but the quantity is surprising even to her. She will have to deal with snipers, bombs and a colleague who is willing to do anything to stop her from finding out the truth. How will Charlie deal with her new job, her new co-workers and memories from the past that are determined to haunt her?