Twelve-year-old Jessie Alden has solved mystery after mystery with her brothers and sister from the cozy confines of the boxcar in their backyard, but now she’s ready to find her own thing. So when a quiet classmate named Daniel shows up at the door of the boxcar with a story that sounds like the start of a mystery, Jessie wants nothing to do with it—even if her friend Charla thinks Daniel is cute. But as things get more complicated (and mysterious), Jessie has to make a big decision: Should she make a fresh start or use her well-honed mystery-solving skills to help someone in need?