Detective Superintendent Tom Bevans has just returned to work after a six months leave of absence. Ten years previously, the love of his life, Dani Lancing, died in horrible circumstances and the recent revelations about the circumstances of her death sent Tom into a very dark place. He is now back in charge of Ares, a unit specialising in sexual crimes. He passionately wants to seek out and imprison those perpetrators who prey on vulnerable young people. It has become an obsession.

The first thing he wants to do is to reopen three cold cases which have never been solved but his boss is less than enthusiastic. Tom turns in a very unorthodox direction and enlists the support of the mother of Dani Lancing. She is equally haunted by finding the truth about the deaths of young girls and goes to extraordinary lengths to help Tom in his unofficial quest. His unit is also very loyal to him and put their own careers at risk to provide information.

In the past Tom was done a favour by Franco, now a big time drug dealer in London. Franco has a daughter whom he adores and who has been brought up away from the truth about her own father. When she is kidnapped and threatened, Franco calls in his debts and Tom is forced to co-operate with Franco to discover the truth. In doing so he finds a connection between the two cases.