In the year 2415, earth-dwelling humans do not live on the land anymore, but within "island cities," structures of metal and crystal, rising like giant mushrooms above the plains of Earth. Most never ever venture outdoors, employing instead, drone-like virtual reality devices to capture the experience for them, convinced that humanity's past environmental misdeeds must never be repeated. The Hagertons of New Allentown, Pa., however, have permission to do so, but their lives will never be the same again, not after father and son, Keith and Jeffrey Hagerton, go on a Sunday autumnal excursion to the long abandoned tourist stop, Crystal Cave, in the once upon a time land based town of Kutztown, Pennsylvania.