"Dead Men's Tales" is a hardboiled detective story that draws from some of my favorite Lovecraft stories, principally "The Case of Charles Dexter Ward." If you've never read it, you should. I'm not gonna go out of my way to explain the finer points of necromancy.
Here's your premise: In 1934 New Orleans, an undead necromancer is blackmailing a family of Creole cannibals. Those cannibals hire a group of clueless investigators to help put a stop to it. Hijinks ensue.