A Safe Place for Dying — Jack Fredrickson

An extortion letter arrives at Crystal Waters, one of Chicago's wealthiest gated communities. It makes no specific threats, gives no instructions, demands only that $50,000 be gotten ready---chump change for an enclave where the cheapest house is worth three million. It's easy to see it as harmless---a note from a nut.
Then a mansion explodes. The homeowners panic, and want it hushed up. If word gets out that a bomber is targeting Crystal Waters, their multimillion-dollar homes will become worthless, a last catastrophe for people strung out from living the good life too well. They hire Dek Elstrom to investigate.

Dek Elstrom used to soar high, too, when he lived with his multimillionaire wife at Crystal Waters, but that was before the dominos of his life tipped over and his ex-wife threw him out. Now reduced to living in a crumbling stone turret, bankrupt of everything but attitude, he's not even his own ideal choice for the job. He's too broke, however, to question the motives of a gift-horse client. He needs the money---and the chance to reconnect with his ex-wife.

Another bomb goes off, and Dek realizes the culprit must be someone who is angry, needs money, and used to live at Crystal Waters. Then he realizes something else. He himself is the prime suspect.