While visiting Michigan's Upper Peninsula to prepare their Great-aunt Sophie's big old house for sale, the Boxcar Children encounter a mystery involving a valuable ring supposedly hidden somewhere in the house.
While staying at an eighteenth-century inn in Vermont, the Boxcar children become curious about the mysterious "accidents" that keep plaguing the owners.
The Alden children suspect that the other guests are somehow involved when things begin to disappear at the bed and breakfast where they are staying in Washington, D.C.