The novel is set in the future. Earth has had interstellar spaceflight for centuries and has contact with numerous extraterrestrial species, which is handled by a department of the Earth government. John Thomas Stuart XI, the teenage protagonist, lives in a small Rocky Mountain town, Westville, caring for Lummox, an extraterrestrial beast which he inherited from his great-grandfather who brought it home from an interstellar voyage. The pet has learned how to speak, and has gradually grown from the size of a collie pup to a ridable behemoth—especially after consuming a used car. The childlike Lummox is perceived to be a neighborhood nuisance and, upon leaving the Stuart property one day, causes substantial property damage across the city of Westville. John's widowed mother wants him to get rid of it, and brings an action in the local court to have it destroyed. Desperate to save his pet, John Thomas considers selling Lummox to a zoo. He rapidly changes his mind and runs away from home, riding into the nearby wilderness on Lummox's back. His girlfriend Betty Sorenson joins him and suggests bringing the beast back into town and hiding it in a neighbor's greenhouse. However, it is not easy to conceal such a large creature. Eventually, the court orders Lummox destroyed. In an amusing scene Westville's officials try several methods to kill Lummox but fail, as his alien physiology appears to be virtually invulnerable to ordinary weapons or poisons, and Lummox does not even realize they are attempting to execute him. Meanwhile, at the Earthgovernment Department of Spacial Affairs, Mr. Kiku, an experienced diplomat, is dealing with the Hroshii, a previously unknown alien race, advanced and powerful, which appear in the solar system and demand the return of their lost child, or they will destroy Earth. A friendly alien diplomat of a third species intimates that the threat is not an empty one. Initially, no one associates Lummox with the newcomers, in part due to the size difference. Lummox is finally identified as important royalty of the Hroshii, as well as approximately female. It turns out that the relationship between John Thomas and Lummox is the only thing that saves Earth from destruction. From her viewpoint, during her centuries on Earth the young but extremely long-lived Lummox has been pursuing a hobby: the raising of John Thomases. She makes it clear to the other Hroshii that she intends to continue doing so. This gives Mr. Kiku, the chief negotiator, the leverage he needs to establish diplomatic relations with the aliens, who normally do not hold regular relations with other species. At the insistence of Lummox, the newly married John and Betty accompany her back to the Hroshii homeworld as part of the human diplomatic mission.
Reception
wrote: Groff Conklin described the novel as "one of Heinlein's most enchanting tales." P. Schuyler Miller found The Star Beast to be "one of the best of 1954."
Editions
All paperback editions and the Science Fiction Book Club hard cover edition omit page 148 of Chapter VIII, "The Sensible Thing to Do", which was in the Scribner's edition and the magazine serialization. In this chapter, John Thomas rereads the entries in his great-grandfather's diary of how Lummox was found. Of significance on the omitted page is that:
The diary skipped a couple of days; the Trail Blazer had made an emergency raise-ship and Assistant Powerman J. T. Stuart had been too busy to write. John Thomas knew why... the negotiations opened so hopefully with the dominant race had failed... no one knew why.
The rest of the page summarizes John Thomas' grandfather's family history, discussing the first John Thomas Stuart, who had retired as a sea captain. The history, as reprinted in the paperback and Science Fiction Book Club editions, then resumes with John Thomas Stuart, Junior.
