Bart obtains the key to the steam tunnels under the school and with Milhouse they go down to check them out. When Bart turns just one of the little valves they find in the valve room the chain reaction causes chaos throughout the school. Bart is caught and Skinner wants to send him to a discipline camp in Oregon. When Bart can’t fly there alone, Homer has to drive him there himself and that is going to cause him to miss the trip to Las Vegas that Moe is sponsoring for all his regular customers. While the boys are gone, Marge and Lisa take some of the boys' old stuff and hold a yard sale, but the only things that sell well are their old medications and that gets her into bit of trouble.