The children are excited about the Founder's Day parade in Greenfield. They decide they will dress like engineers, and Grandfather will pull the boxcar with his truck. So they begin a major cleanup, inside and outside, including new paint. Of course their dog Watch is 'helping' too. Two different men come by and offer to buy the boxcar for their train collections, but of course the children say NO. One of the men is apparently allergic to dogs, because he keeps sneezing. After they finish, they can relax for a few days before the parade. One day Benny gets worried because Watch hasn't eaten his breakfast, so he goes out looking for him and discovers that the boxcar is also missing! Someone has taken their boxcar, possibly with Watch inside it, since they have no luck finding Watch either. There are several suspects, including a very spoiled little girl who throws a tantrum because she wants it for a playhouse, and even their friend Sam, the ice cream man, whose wagon has been all smashed up. Of course all eventually ends well, and their friend Sam, who is still working on getting his wagon fixed, ends up having his horse pull the boxcar in the parade.