Helen’s idyllic life—handsome architect husband, gorgeous Victorian house, and cherished baby on the way (after years of trying)—begins to change the day she attends her first prenatal class and meets Rachel, an unpredictable single mother-to-be. Rachel doesn’t seem very maternal: she smokes, drinks, and professes little interest in parenthood. Still, Helen is drawn to her. Maybe Rachel just needs a friend. And to be honest, Helen’s a bit...