The Road to Eden is Overgrown (Leveller Trilogy #1)

After losing his wife to cancer, Nicks, a broken man, tries to drink himself to death but a mysterious encounter one evening sets his life on a completely unexpected path.
When DCI Thurstan Baddeley takes over at the lively and resourceful murder squad all hell seems to break loose in and around the city of Liverpool. A local crime lord is gunned down in a quiet backstreet and a string of execution-style killings follow which lead the investigators to discover hidden clues pointing to something much bigger than organised crime.