While they are at the dog show, the Aldens notice that a valuable prize dog, a champion English setter, has been stolen from the show. They decide to help the dog's owner, Mrs. Hastings, find her dog. The Aldens use their detective skills to gather clues and track down the missing dog.
As the Aldens investigate the dognapping, they find themselves in danger. Someone is trying to stop them from finding the missing dog. They must be careful not to get caught, or they may not be able to save the dog.
The Aldens work hard to find the clues that will lead them to the missing dog. They interview the other dog owners and workers at the dog show. They also search the fairgrounds for any sign of the dog.
Finally, the Aldens find the missing dog. They track it down to a nearby animal shelter. The dog has been drugged and left at the shelter. The Aldens call Mrs. Hastings and tell her that they have found her dog.
Mrs. Hastings is very grateful to the Aldens. She thanks them for their help and offers them a reward. The Aldens refuse the reward, but they are happy to have helped Mrs. Hastings.
The Aldens have solved another mystery. They have helped Mrs. Hastings find her missing dog, and they have brought a criminal to justice.