Venus Flytrap by Russell Watson

Joey Netherhill is an accidental P.I. Life, it seems, has dealt him a series of Aces and Jokers, the latter being a vindictive C.O. in the Marines and a shrew of a Glasgow-born wife. Escaping from his former life - and wife, he finds himself entangled by the low-life in a town in the south of England. Then an ace is dealt in the form of a police detective who believes his pretty girlfriend is having an affair and requires the assistance of an 'off the books' investigator. Joey finds the solution to this puzzle leads him into a world of danger far beyond his capabilities or comprehension. He is confronted by forces of evil that will swat him as easily as a fly. But Joey Netherhill has other ideas about that...