Old Tin Sorrows (Garrett, P. I. Series #4) by Glen Cook
When his old friend Blake Peters calls in some overdue favors. Garrett feels like he’s committed himself to a corps of corpses. Someone is trying to kill Blake's wealthy, retired General Stantnor, in a most lingering, painful, and maybe poisonous way. Can Garrett keep the general above ground?
But Stantnor's mansion holds a host of surprises for a human detective who thought he'd seen it all. For while the general is dying slowly, his employees are losing their lives at a far speedier rate. And when some of the not-long-departed try to enlist their comrades in the growing legions of the dead, Garrett knows it's time to call in his own troops—in the person of Morley Dotes, the toughest half-elf around. With Morley guarding his back, Garrett's got to handle—or gets his hands on—both the killer and the mansion's two elusive beauties, who seem invisible to everyone but Garrett!