Arthur had a job to collect coins for Mrs. McGrady to raise money for a new dog for the Elwood City firemen, and when he left the bag of quarters where Mrs. McGrady was working, she said she never received them. While this was happening, Buster opened his detective agency, he has no idea his first job will involve Arthur. Now, it is up to Buster to solve this mystery, was Arthur the real thief?....

When Arthur is teased by Francine and the others because he hasn't lost all of his baby teeth yet, he becomes determined to lose his tooth and fit in with the others.