Not content with a flickering jack-o'-lantern for Halloween, somebody has torched the old Hopkins Homestead. It's the fourth case of arson Tinker's Cove has seen in five months, and the most deadly, since Homesteader Monica Mayes, enjoying a rare off- season overnight stay at her summer house, was killed in the flames. Whodunit? The obvious suspect for Lucy Stone (Tippy-Toe Murder, 1994, etc.) is the widower, Dr. Roland Mayes, who's been extending his gynecological research to bodybuilding bimbo Krissy Wright. But would Mayes really go to the trouble of burning down all those other buildings in preparation for offing his inconvenient wife? Forget the mystery; the burning questions here (and the only time the tale flickers to life) concern the commercialization of rural Maine, the need of older drivers to turn in their licenses, and the breast-feeding of Zoe, the latest among fecund Lucy's progeny.