Inside a time capsule, Brian and Sean discover a decades-old mystery

In 1918, the people of Redoaks buried a time capsule full of messages for the future. Besides all the grown-up stuff, the fourth-graders of 1918 included a packet of letters to the fourth-graders of today—which means Sean Quinn is about to get a letter straight from the past! But when it comes time to crack the capsule's seal, Sean and his brother Brian learn that its contents could change the town's future forever.

Boris Vlado, the only surviving member of the fourth-graders of 1918, warns the boys that the time capsule holds a dangerous secret. But when they open the capsule, there's nothing inside! To find out why, Brian and Sean will have to solve a historic mystery that involves bank robbery, corruption, and the most valuable stamp collection Redoaks has ever seen.