It is the summer of 1961, and eleven-year-old Arno Creelman wants nothing more than to be an astronomer. Fortunately, his struggle with claustrophobia has little impact on his one true passion. Unlike his annoying friend Buddy, who wants to become an astronaut and is not at all bothered by the idea of flying in a cramped space capsule, Arno dreams of exploring the galaxies with powerful telescopes back on Earth.

But first he has to enter a local radio contest and win a visit to the new observatory that is about to open near his town. The ribbon will be cut by Arno's idol, Jean Slayter-Appleton, a renowned astronomer whose weekly columns he clips for his own notebooks. When he finally manages to phone in and correctly answer the skill-testing astronomy question, which earns him an invitation to the opening, Arno is thrilled.

Then a new boy moves to the neighborhood, and he seems to challenge Arno in every way. Robert even believes in astrology, which Arno argues is not a science at all.

Before long, Arno is feeling left behind, on the outs with his friends and even abandoned by his beloved dog, Comet. And when Robert informs him that he has already been to an observatory, and tells Arno what the experience is actually like, Arno's dream becomes a cosmic nightmare.