August 1955 Howdy Doody adopted Heidi as his sister. She became a part of the "Howdy Doody Show" after he called his friend, Dilly, saying he won't be going to the movies as they usually do. When he did, he told Dilly that he has business to take care of. When Dilly enters the soda shop, he spots Howdy and Heidi and mistakenly believes that Howdy has a girlfriend. He leaves and goes to Inspector John J. Fadoozle.

At John's office, Dilly explains that Howdy has a girlfriend. John doesn't believe it. Dilly tells John, Howdy and the girl are at the soda shop. John goes to investigate and spots Heidi in a phone booth having a phone call. John listens to Heidi's conversations about the munition factory, the dam, and the power supply that she saw. She said she has not seen all of Doodyville yet. But, she'll tell them about it when she does.

John believes Howdy has fallen for an enemy spy. He runs to get Dilly to help. They'll start to follow and shadow them. They spot Howdy and Heidi walking together as she asks if he has trouble getting his friends to join the party. Howdy thinks not. Dilly thinks she wants Howdy and them to join her gang.

Suddenly, John jailed Heidi.

Eventually, Howdy explains that it was the coming-out party for Heidi as his adopted sister, much to Dilly and John's surprise. Dilly said he thought Heidi was Howdy's Girlfriend. Howdy laughs at what Dilly thought. John and Dilly apologize for their mistake and join the party with Howdy and Heidi.

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