The Happy Hollisters are excited about the upcoming autumn season, with plans for pumpkin decorating, bobbing for apples, and the Shoreham Halloween parade. They decide to host a party for their friends and Farmer Johnson offers the use of his barn for the festivities in exchange for the children's help selling pumpkins at his farm stand. The mysteries begin almost right away, when the horn on Farmer Johnson's old Model T Ford begins to blow...