What is there in Sam's past that makes this mystery so hard to solve?
When their friend Sam gets a letter full of riddles from an eccentric millionaire, the Alden children are eager to help him crack the code. If Sam can solve the puzzle in time, he will inherit the millionaire's money. But Sam isn't the only one in town to receive such a letter, and whoever solves the mystery first will win the prize. The Aldens want to help their friend, but solving the millionaire's mystery turns out to be even harder than they expected.