Crickets on the Moon is a story of friendship, family, and the power of determination and cooperation in overcoming obstacles. Sirius has traveled halfway across the galaxy. He's a diplomat-in-training with an unusual deformity, desperately trying to make good on his father's dying wishes. He doesn't know it, but his deformity is also the source of a potent gift he possesses. After two failed missions, time is running short, and it looks like he's going to have to return home in shame and face possible exile. Before he embarked on his journey, his uncle told him to "find the right planet, find the right contact," but he's found neither, until he comes across Earth, hoping he finally got it right. He selects Jonah, a 13 year-old boy who is dying from leukemia, for his mission. Sirius parks on the moon and sends a mysterious orb to Jonah, who must figure out how to use it and also demonstrate, along with four other boys chosen by Sirius, that people on Earth can responsibly use power for peaceful purposes. The boys form a club that meets nightly with the orb, with the directive to ask one question a day, and to choose their questions carefully. It will answer any question they ask.

Besides Jonah, there's his hyperactive best friend Ricky, Steven, a socially challenged science geek, Todd, Steven's mortal enemy and a troubled, unhappy boy with dark secrets, and Joe Billy, one-quarter Arapaho who's tried to distance himself from his heritage and the teachings of his grandfather in order to better fit in with his peers. The success of Sirius' mission is constantly challenged by his own emotionality as well as by the boys' struggles in their own lives and with each other.

The mission culminates in a perilous adventure in the Rocky Mountains. Sirius must decide whether to risk the boys' lives or to risk never being able to return home. Ultimately, the boys, including Sirius, learn the deeper meanings of friendship and family, and discover a greater purpose to their lives.