Lucas Davenport had reason to be relieved when he was called off a morals case -- involving a Minnesota state senator accused of having sex with a minor -- and assigned to a double murder. For one thing, the killing of affluent widow Constance Bucher and her maid isn't politically sensitive; for another, it seems like a prosecutorial slam-dunk. The messy crime scene looks like the calling card of drug-addled thieves who, like many others before them, blundered into a situation they couldn't control. Looking closer, though, Davenport detects the scent of more sophisticated plunderers. And then the other murders begin…