Adventures in the Northwoods Vol. 7: Grandpa's Stolen Treasure

At the end of The Mysterious Hideaway, Kate's mother received a letter from the Nordstrom's Swedish grandparents that told of their plans to travel to America to find their son Ben. The Nordstroms miss their train stop, and when non-English-speaking Grandpa tries to get help at the Union Depot, Grandma vanishes under mysterious circumstances!