Nine-year-old Sebastian Duncan returns from a near-death experience with the startling news that his mother Jenny appeared to him and said that, no, she didn't take an accidental overdose of sedatives at a house party last year--she was murdered. After this arresting opening, though, the story seems to go into cardiac arrest. Jenny's mother, Elizabeth Hollander, is the only person Sebastian's told his story to, and since she won't let the D.A.'s investigator Arlene Flynn (A Grand Night for Murder, 1995, etc.) interview Sebastian directly, Flynn is stuck with an unlovely slog through motives and alibis for a dozen party guests. When none of the dramatis personae has any more personality than a checker, puzzles like this stand or fall on ingenuity alone, and this one falls with a thump. Instead of developing his plot, Jeffers grafts on another one--a murdered widow whose killer took the trouble to carry her body out of her house--that shows Flynn's talent for close observation en route to a disappointing solution, and pads the whole mÇlange with reveries of classical music and more quotations than Bartlett's. The net effect is of sharing the company of an intelligent, well- read detective who's telling you everything that happens to be going through her head. Enough mystery for one and a half short stories. The susurrus of references to the longer genre may be a plus for some mystery-lovers, although it put at least one of them into a deep sleep.