This is a standalone crime novel, but Matt Arlidge has apparently built his name and reputation on a series of books with the central character, Helen Grace.

The theme here is centred around there being just nine individuals in the UK who have been granted lifelong anonymity, for their own safety, because of their terrible crimes.

So what would happen if someone exposed the true identities of these individuals to the families of their victims, where those family members are desperate for revenge?

This novel explores numerous incidents where this is the chain of events.

There are two central characters - the detective seeking to find the source of the leak and prevent further attacks, and the probation officer Olivia Campbell who is caught in the midst of the threat. It is her responsibility to keep the criminals' identities secret and ensure their safety. 

Despite the many characters, locations and events, this is a gripping read. The chapters are short and punchy, and you can't stop reading. It's also hugely thought-provoking regarding vengeance, forgiveness, redemption and justice. Excellent.