Small-scope horror tale set in Manhattan by the author of Reprisal (1991), Reborn (1990), and The Keep (1981). A diversion from Wilson's malignant-entity series (see Tessier, above), not to be confused with the new television sitcom Sibs. The twins Kara and Kelly Wade, once as pert and bright as the Doublemint Twins, are now into their thirties. They've parted. Kelly's a nurse at St. Vincent's Hospital in Greenwich Village, while Kara's home with a degree in women's studies, writing a feminist book. Kara fled Manhattan because, secretly pregnant with a Manhattan cop's baby and knowing the cop would never leave hateful New York, she's had their daughter, Jill, without telling him. Now Rob Harris, the cop, is a detective in Homicide and calls Kara to tell her that Kelly has fallen from the twelfth floor of the Plaza under grisly circumstances. Kara identifies her sister's vastly mutilated corpse, then uncovers a secret life around Kelly. Kelly had a multiple-personality disorder, according to her psychiatrist, Dr. Gates, and as ``Ingrid'' would put on a red- leather minidress, pick up men in the Plaza Hotel's Oak Bar, then, upstairs in her room, have sex with them gratis, often two at a time. During one of these scenes a lover bit her shoulder. The pain drove out Ingrid, and horrified Kelly found herself servicing two men and leaped through the window. Now, does Kara have the same personality disorder, produced by the same childhood trauma (incest with their father) that Kelly had revealed under hypnosis? Kara goes under hypnosis as well and indeed a new Kara, ``Janine,'' appears and starts writing notes to Kara. Janine, too, is a post midnight sexpot. But we quickly sense that Dr. Gates has faked the twins' disorder and is himself ``Ingrid'' and ``Janine''! Or is he, too, being directed by an evil entity? Kara's nine-year-old Jill, a budding feminist, has all the novel's best lines, especially when objecting to the cleavage in a Penthouse she finds in Rob's bathroom. Otherwise, standard stuff.