Mystery of the fallen treasure / Warner, Gertrude Chandler

During a trip to Oregon, the Aldens are astonished when Watch discovers a backpack filled with valuables, a finding that compels them to learn what happened and return the backpack to its rightful owner.

The Aldens, and their dog Watch, find a backpack full of jewelry and when they try to return it to the owner, find that it has fallen from a plane.