Had it really only been a year since the Double Cousins solved their first mystery? But now back at Grandpa's ranch for their summer visit, it seemed something was missing-one of those exciting mysteries. For the first time in a year, they were all together again, and the time was slipping by with no mystery. If this was the new normal, they didn't like it very much.

Then out of the blue, strangers arrive at the ranch and drop a mystery right into their laps, shocking even Grandpa with ranch history he had never heard.

The Happy Hollow school property was originally part of Grandpa's land. Had the first one been a sod building? Can they fulfill the dream of a centenarian by recovering its history and, against all odds, find the tiny time capsule hidden by two young boys over 120 years ago? And can they put up with an annoying visitor who doesn't like the ranch or anything on it?

In the seventh Double Cousins Mystery, the cousins, including Brandon, use all their sleuthing skills-along with some new ones-to help that family of strangers find the answer to their mystery; and in the process, they learn that mysteries truly are a part of history.