Twelve-year-old Nova is eagerly awaiting the launch of the space shuttle Challenger⁠—it's the first time a teacher is going into space, and kids across America will watch the event on live TV in their classrooms. Nova and her big sister, Bridget, share a love of astronomy and the space program. They planned to watch the launch together. But Bridget has disappeared, and Nova is in a new foster home. While foster families and teachers dismiss Nova as severely autistic and nonverbal, Bridget understands how intelligent and special Nova is, and all that she can't express. As the liftoff draws closer, Nova's new foster family and teachers begin to see her potential, and for the first time, she is making friends without Bridget. But every day, she's counting down to the launch, and to the moment when she'll see Bridget again. Because as Bridget said, "No matter what, I'll be there. I promise."