Marcia Willet's "A Week in Winter" and "A Summer in the Country," her first two novels to be published in the United States, were welcomed enthusiastically by both eager readers and appreciative reviewers. Her new novel, "The Children's Hour," will not only delight her current ardent fans, but will garner Marcia Willett a whole new circle of friends. "The Children's Hour" is set in a big old rambling house overlooking the sea, where assorted small...