Percy more often gets the dirty jobs involving trucks and longs for a washdown just like any other engine. Unfortunately, when he goes to the washdown, Percy and the other engines are informed by the Fat Controller that all engines can only have one wash per day due to a water shortage. He then tells the engines that usefulness comes before cleanliness. Percy is annoyed at this as he thinks that Gordon only needs a washdown to feel important. Gordon points that he is important as he pulls the Express.Percy returns to work, determined not to get dirty, but the trucks had other ideas and give Percy a difficult time; they pull him right under the coal hopper, and on their way to Callan, the trucks tease Percy by calling him "Dirty Percy". At Callan, Percy shunts the coal trucks into a siding, right alongside Harold who is unloading medical supplies. Harold takes off, spreading cinders and ashes all over Percy. His driver reminds Percy that usefulness comes before cleanliness, but Percy still longs for a clean job. The driver suggests that they were to take vans of sugar to the chocolate factory. Relieved, Percy agreed to take the vans.Percy finally gets to do a clean job, but he does not notice that a patch of oil in the siding which leads to the chocolate factory. Percy slips on the oily rails and crashes through the wall right into the chocolate factory and out the other end. He is covered in sticky gooey chocolate.When Duck brings Percy back to the sheds, Thomas, James, Henry, and Gordon tease Percy on being covered in chocolate. The Fat Controller knows how much work Percy had done despite his problems and has proved that usefulness does comes before cleanliness. As a reward, Percy is to be rewarded with a washdown and a new coat of paint, and Percy couldn't be anymore happier.
Tropes featured in the episode:
- All of the Other Reindeer: The engines and the trucks alike teased Percy throughout the entire episode.
- Butt-Monkey: Percy.
- Earn Your Happy Ending: Percy followed the "usefulness before cleanliness" principle despite the ridicule from the engines and the troublesome trucks. At the end of the episode, The Fat Controller rewarded him both a washdown and a new coat of paint.
- The Freelance Shame Squad: The other engines when they saw Percy covered in chocolate:Thomas: You look good enough to eat!
James: Pudding Percy! ("Bon Bon Percy" in the US version)
Henry: Choc-ice on wheels!
- Karma Houdini: The engines and the trucks.