The secret of the old mill

Two brothers wander the bustling Bayport train station, hoping to greet their famous detective father after weeks apart. A hurried stranger asks them to change a five‑dollar bill, and the boys’ quick kindness sets off a chain of small adventures—shopping for pie‑plates, swapping baseball bats, and chatting with the genial shopkeeper, Mr. Moss. Their ordinary afternoon takes a sudden turn when the stranger’s mysterious friend disappears, leaving behind a cryptic clue that points toward the long‑abandoned old mill on the edge of town.

Intrigued, the brothers decide to investigate the mill, a place whispered about by locals for its creaking wheels and hidden passages. As they explore its dusty interior, they uncover odd footprints, a locked chest, and hints of a secret that someone will do anything to keep hidden. The mystery deepens, and the Hardy boys must use their wits and teamwork to untangle the clues before danger catches up with them.