A cool, smart, and stylish first thriller--St. Thomas-set--of murder plot and counterplot that features a major twist in nearly every one of its 18 tightly woven chapters. After a preface set 20 years back, detailing the discovery by a Long Island postman of a dead woman and, clutching a knife and saying, ``I killed her,'' her bloodstained little girl, Savage moves to today's Caribbean. Right away, we read that ``The idea of murder, once formed in her mind, simply would not go away.'' In whose mind? Well, many readers will ignore the ellipses at the end of the first paragraph and, going on to read that ``Kay watched the girl from her chaise lounge...,'' will assume that the potential murderess is Kay--though it's soon revealed that Kay is the intended victim, and ``the girl'' the killer--just one tiny way in which Savage plays with prose-and-plot conventions to spin expectations around. The girl, a young beauty calling herself Diana Meissen (like most everyone here, she's not who she claims), gets herself hired as governess to Kay's daughter--and that night is kissing Kay's handsome, middle-aged husband, Adam: ``I wanted so much to call you....'' Are Diana and Adam planning to kill Kay? So it seems--especially when Adam commits a series of robbery-slayings in order to blame Kay's death on a homicidal thief. But how do these killings relate to identical ones ten and twenty years before? How do they tie in with the young man, allegedly a real- estate developer, who's spying on Diana? Or with the girl who held the knife years ago? Surprise piles upon surprise, logically, convincingly, until all secrets--revolving around an old family horror--are resolved in a climax that owes a debt to Greek tragedy. Not so much suspenseful as intellectually satisfying: a finely wrought, unusually clever literary debut--and a natural for the movies.