Tell the plumber that his princess is in another castle
Once upon a time, there was a princess that lived in a castle. The only problem is, it is impossible to tell one castle from the next as far as which one holds which specific princess. Say that five times fast! Regardless, convincing the plumber he has gone through his own trials and tribulations in one castle only to find out the princess he is trying to rescue is somewhere else is going to be one of the tougher quests your hero has ever set out to accomplish.
This quest will measure the hero's wisdom, patience, and determination. Your hero must be able to find the plumber in order to let him know he's at the wrong place, searching the wrong castle, and will not find the actual princess he is looking for. This quest can take awhile to complete, depending on the ability of your hero to first find the plumber in question as well as to then convince the plumber he needs to start over in another castle.
Tip: Giving the plumber a set of green overalls makes him less likely to argue with your hero.