You can't go home again, magazine reporter Kay Engels learns when she flies up to Falls City, New York, for her high-school reunion-- only to find her old flame Chris Campbell happily married, his thrice- married cousin Terry carrying on with ever-infatuated Richie McDowell, and a third Campbell cousin, Tony, having to break off his chastely budding romance with Kay when he's accused of Terry's murder. Follow lots more suspicious doings--from Terry's escort revealing well-earned ties to the Chicago mob to Tony's beloved aunt Maggie Prestwick's plan to give her rundown farm back to the Indians--but nothing dampens Kay's spirits for long (``It was a good day, wasn't it? In spite of everything,'' Tony tells her a few hours after finding Terry's corpse), not even the news that she's adopted, or Chief Al LaForge's announcement that Tony is the killer. We know better; it must be somebody with much less nice manners.... Even if first-novelist Stein's Pollyanna-ish prose doesn't capture the Mary Higgins Clark crowd, it's sure to appeal to Nancy Drew loyalists. Maybe you can go back to high school again--especially if you've never left.