When Stephanie Lewis finds secret writing in the margin of an old book in the library, The Math Kids have a new puzzle to solve. But first, they must learn about codes and ciphers and how they can use their math skills to solve them. As one clue leads to another, the kids are drawn into the mysterious old house that overlooks the town. Is it really haunted like some townspeople say? And who is the man with the long beard who keeps showing up everywhere...