The plot concerns a young boy, Jon, who accidentally 'falls' to Earth through the titular portal. Accustomed as he is to his utopian, pacifistic, vegetarian, and money-free world, Jon's bewildered attempts to connect with the petty grievances of Earthlings serve as foil to the reader; and while there is some action and suspense, the main tension of the story comes from the sympathetic family that shelters Jon being forced to confront their own complacency towards the injustices of their world while trying to make Jon understand that this is just how life is — but of course, for Jon and his world, it isn't.
Considering the state of the world in 1965, the book sends a clear message that the future, and we humans, can, and must, be better.
This book provides examples of:
- Adults Are Useless: Averted. Most of the book is about the Beans trying to help Jon.
- All of the Other Reindeer: The Pitts and Macklins hate John because he seems strange to them.
- Aliens Speaking English: Averted, though he is a very quick learner.
- Captured Super-Entity: The government tries to make Jon into one.
- Fluffy Tamer: Jon manages to play with Rascal, the dog Thomas Bean had just about given up on taming.
- Good Cannot Comprehend Evil: Averted, but Jon has a lot of culture shock about the deception and violence on Earth.
- Good Is Dumb: The Beans use Jon's telepathy to clear him of a charge of theft, without thinking that the government might try to kidnap Jon for devious purposes. Earlier when Thomas asks if they should ask for advice Mary Bean only worries about reporters.
- Identity Amnesia: After falling and hitting his head, Jon forgets who he is and where he came from.
- Human Aliens: Jon.
- In Which a Trope Is Described: Each chapter title is a sentence beginning with "He..." as in "He is Lost and Found" and "He Gains a Home."
- Keeping Secrets Sucks: Jon is unhappy with the idea of pretending to be the child of a friend of Thomas Bean.
- Lawful Good: Deputy Anderson Bush is the "Law Before Good" flavor; his investigation of the theft of some items is what drives Jon to expose his telepathy to the world.
- Living Lie Detector: Due to his telepathy. It becomes a problem later on.
- Telepathy: Jon is able to read others' minds as well as animals.
- Powered by a Forsaken Child: The author never explains exactly how the U.S. government wants to use Jon's telepathy, but it doesn't sound good. Mary Bean thinks it might involve warfare.
- Small Towns: The Beans live in a small town, and everyone who grew up there knows who is related to (and will provide an alibi) to whom.