A stranger named Raoul Meridian invites spoiled beauty Nadine and her shiftless fiancé, Albert, to spend a weekend at his ''ponderous...and truly alien'' mansion in the desert. It's pretty clear that no good can come of this odd, unhappy gathering. Sure enough, within hours of their arrival, Nadine has fallen under the spell of the harsh California landscape and her loathsome but intriguing host. Albert, coming completely unhinged, rides off into a nearby canyon in pursuit of a mysterious child named Destina. The 94-year-old author's roots as a surrealist painter are evident throughout her creepy, erotically charged first novel. Dorothea Tanning's image-driven prose isn't always easy to follow, but like Meridian, Chasm: A Weekend is ''a monument of puzzling freakishness.''