Twelve-year-old Sam likes to memorize fun and weird facts. She's constantly spouting quotes from her fact books, such as the size of the largest bubble-gum bubble blown through the nose or how jelly gets into a donut. But Sam does not like the fact that she has to spend a month of her summer vacation at her grandparents' place while her parents are away!

She adores her grandmother, but Grandma will be at work most of the time, leaving Sam with the Colonel, her prickly grandfather. Sam's relationship with him is shaky at best, and now that the Colonel has had to retire from his career as a military pilot, he is harder than ever to get along with.

Sam soon finds that her grandfather's behavior is even stranger than she expected. He keeps disappearing into the woods for long stretches of time and won't let Sam go into the old barn. Obviously the Colonel is hiding a big secret, and Sam is eager to solve the mystery. Reluctantly she accepts help from Billy Burnham, a classmate she can't decide if she likes or hates. Together they discover that the Colonel is building an airplane. Will Sam let the cat out of the bag and ruin her grandfather's plans? Or will her grandfather relent and let his granddaughter help him finish the plane?