This appears in her collection, Sinister Tales.
Boris is not a very nice guy. It's not that he cleans human skulls for a living but that he steals them and... well, makes his own out of those he doesn't like--homeless men and women who don't want to have sex. He meets an older woman, Bea, who's willing to make illegal skulls with him. The problem comes when he and Bea try to make illegal skulls from where the homeless hang out. They're waiting.
A nice--or not so nice--twist pounces you at the end--both tender and gruesome--that makes up the rest of the tale take on a brighter, more resonant hue.