Hey, pimping ain’t easy but here it goes: Chelsea Cain’s newest in the Archie Sheridan and serial killer Gretchen Lowell series is EVIL AT HEART (September 2009). It is the third book in the series that started with Heartsick. If you haven’t read these books yet: what are you waiting for?
[snip] Here Gretchen is still on the loose and Archie is still hospitalized after his ploy to catch her went spectacularly wrong. They’ve entered adetente of sorts—Archie agrees not to kill himself if she agrees not to kill anyone else. But suddenly there’s something else to contend with that might be worse—a zealous fan of Gretchen’s, paying homage to the Beauty Killer by luring Archie and reporter Susan Ward to the scene of a grisly murder. At least they hope it’s the work of someone new, for the prospect of Gretchen breaking her promise is more than Archie can bear.
Updated for better clarity.