When NYPD detective Callum Doyle's partner is murdered, and then his replacement is also brutally killed, suspicion falls on Doyle himself. Then he receives an anonymous message: This is just the beginning. Anyone he gets close to will die – and that includes his family. Desperate to find out who is responsible, but with his every move putting others in danger, Doyle has to ask himself: how low would he sink in order to get his life back?

The first in a new series featuring Callum Doyle, an NYPD detective with a secret past