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 Children begin to wonder how this Seattle puzzle came to them. As each riddle brings the children to a new part of Seattle, the children try to piece the clues together. Who is planting the riddles, and what will happen if they can't crack the next one? Where will the final riddle lead them?