The novel begins on a wintry March afternoon in the isolated white farmhouse where the Murrys live. The one unusual room of the house is the laboratory where, as established in previous books, the Murry parents, both famous scientists, do research into polymers, virtual particles, and quasars. By messing around with their father's computer, Sandy and Dennys, the Murry twins, are transported to a hot, barren wilderness, where, almost immediately, they are badly burned by the blazing sun.
When the twins are rescued by a tent-dwelling family of small brown people who help them heal, they discover that, in this new world, humans live for hundreds of years and that several of them converse with their god, whom they call "El." It is some time before the twins learn that the "patriarch" of the family that takes them in is Noah and that the world will shortly be destroyed by a flood of "many waters."
The world is also populated by a number of creatures which Sandy and Dennys have always assumed are mythological, such as the unicorns who rescue them on several occasions and eventually take them back home. In addition, the twins encounter the golden seraphim and the beautiful white nephilim, winged, angelic beings who, at times, take on the forms of various animals. During the course of the novel, the twins grow to appreciate the simple lifestyle of Noah and his family and, when they finally return home, honestly miss Noah's family and their world.
(The entire section is 248 words.)