Death Hampton by Walter Marks

Book 1 of the Jericho series.
Introducing tough, street-wise NYPD detective Neil Jericho, burnt out after years working violent homicide and drug cases in East Harlem, he transfers to the police department of peaceful, posh East Hampton.

Detective Jericho is called upon to investigate the disappearance and possible drowning of Burton Cascadden, a wealthy real estate developer. As he uncovers evidence that this may be a homicide, Jericho becomes attracted to a suspect — Cascadden’s wife, a beautiful modern dance teacher. She responds to him as well, but are her feelings real? Or is she manipulating him? Jericho begins to lose his objectivity, which complicates an already baffling case.

“Death Hampton” is a murder mystery in which readers know, or think they know whodunit, while the detective does not. However, in the end, it turns out that nothing is as it seems.