Fifth-grader Star Bell has a date with Logan, a nosy best friend, and two very big secrets. Logan promises her secret adventures. His promise is broken when Crystal figures it out and wants to join in. Along the way, Star discovers that her other secret might change the world.
Star, Logan, and Crystal explore a magical portal to make-believe realms of adventure, mystery, and danger. In a virtual world created by a secret book-reading research computer called SIMMER, they can participate in any storybook adventure they choose. From a turbulent flying carpet ride fleeing an evil magician, to swashbuckling sword fights with lusty pirates, to a frightening encounter with the ghost of an orbiting space stationits a dream come true for the three friends.
But their fun may come with a catch. Their adventures differ from the storybook versions, and Star suspects their make-believe actions might actually cause harm in the real world. The only way Star can persuade her friends of the potential gravity of their situation is to lead them on a daring adventure of her choice. Risking real harm if she is right, hoping she is wrong, will she reveal the one secret that may explain everything?