Harris (The Masada Plan) knows how to refurbish a thin, standard, but always serviceable suspense plot; what he doesn't know is how to keep his trendy embellishments--cute talk, sex talk, angst talk--from sinking the whole shebang. Sam Schroeder, divorced father and hack magazine writer (a ""clever minor prig"" to his friends), takes kids and grandma off for a weekend of attempted rapport on Nantucket, where he runs into a scared, young, messily attractive waifette: heart-to-heart talk followed by sex on the beach. Next day some mob thugs kidnap Sam's kids and drop a note--""IF YOU WANT YOUR KIDS, GIVE US THE GIRL""; the girl of the one-night stand, you see, is the daughter of a murdered special prosecutor in Boston, and she's carrying a notebook full of hot evidence. What is poor Sam, who's always been afraid of confrontations, to do? In the book's nicest touch, he unheroically locates the girl, hands her over to the hit-men, and heads for home with kids and grandma. . . but, more routinely, turns back at the last minute. His rescue mission--some underwater stuff--fills out the familiar scenario, but not until Sam's Nantucket allies, an insufferable married couple called Rocky and Stoney, have joined him in a tediously extraneous session of sex-confessions and psycho-baiting (hand-me-down Who's Afraid of Virginia Woolf?). By trying too hard for the chic-repartee, identity-crisis audience, Harris pretty well mucks up what could have been a competent cat-and-mouse with nice shadings of character.