Shadow of Death - William G. Tapply

Suspicious that his candidate's husband might be having an affair, the campaign manager convinces Boston attorney Brady Coyne to hire a discreet private investigator to find out what is really going on before the campaign itself is derailed. Brady is normally reluctant to get involved in this kind of domestic situation but the candidate is an old friend who has asked for his help personally. Hopeful that any odd turn of behavior will be easily explained away, Brady hires a former undercover cop turn P.I. to tail the possibly-errant husband.

What appeared to be a simple situation quickly turns deadly when Brady first gets a cryptic call from the P.I. and then the P.I. is found murdered in a car crash clearly staged to make it appear to be an accident. Since Brady is barred by attorney/client privilege from speaking to the police - and his client has refused to relinquish privilege to allow him to do so - he takes it upon himself to find out what has happened to the still missing husband and the people responsible for the murder of his colleague. From Boston's North End to the pastoral village of Southwick, New Hampshire, Brady's quest to uncover the truth leads him to face the deadly consequences of a decades-old tragedy.