Blood in the Water by Jane Haddam - Paperback Mystery

Martha Heydrich lives in a very big, very expensive house in Waldorf Pines, a very rich, very gated community west of Philadelphia. She drives a flashy pink sports car, joins all the local commitees, sticks her nose in everyone's business―and gets on everyone's nerves. She is also, it is rumored, to be having an affair with a local teenager. The very same teenager who is discovered one night―by Martha's husband―floating dead in the community pool…

Besides blood in the water, there's a fire in the pool house―and another corpse. The police assume the charred remains belong to Martha Heydrich, since she's nowhere to be found. But when DNA tests reveal it isn't Martha at all, but an unknown man, they turn to ex-FBI agent Gregor Demarkian to get to the bottom of it. The killer could be a jealous husband, runaway wife, or psychotic neighbor. But whoever is guilty, Demarkian wants to make sure their next gated community is a maximum security prison…