The Aldens are on vacation in Seattle They're ready to explore the city, and one of Grandfather's friends is going to give them a personal tour. On their first day of sightseeing, they start the day at the Hungry Heart Diner where a mystery falls right into their laps Benny finds a riddle taped to the bottom of their table. What does the riddle mean, and where will it take them? When the first riddle leads the children to another riddle, the Boxcar...