Nancy Clancy and her best friend, Bree, are off to solve another mystery, but this time it involves going back in time! As Nancy’s class learns about time capsules in school, another relic from the past pops up in the present. When Nancy finds an old desk at a tag sale, she soon discovers that someone left behind a key. Nancy and Bree set out to unlock the secret of the silver key in hopes of finding some treasure along the way. But unlocking the mystery soon proves to be harder than they had thought, and when the answer isn’t what they expected, they learn there are some things that remain timeless forever.