Sleeping Dogs — William Paul

Introducing Detective Chief Inspector David Fyfe, a tired Edinburgh cop whose disregard for law enforcement by the book is both his strength and his weakness. Too far into middle age, too lax about his marriage vows, too fond of booze, and too sarcastic to be popular among the department higher-ups, Fyfe would love to resign. But he can't - too steep a mortgage.
Fyfe has owed the chief constable a favor ever since he saved Fyfe's job when Fyfe undoubtedly deserved to be fired. When the chief presents him with a particularly sticky case of funds missing from a church treasury, Fyfe knows he can't refuse. Furthermore, when a priest's murder connects this penny-ante parish theft to a homicide and drug ring investigation Fyfe helped to crack eight years before, he sees an opportunity to prove his worth again as a homicide detective. If only he weren't so involved with the beautiful but manipulative woman who turns out to be the main suspect...