Thomas and Duck were at Tidmouth Sheds with Daisy, BoCo, and Class 40 having conversations which don't interest Class 40 at all. Just then, Percy comes in all filthy and complaining about it. The diesels decide to tell about their mistakes. Daisy goes first.
Daisy is a very highly-sprung engine that hates unpleasant smells. After dealing with coal and soot from a blue tender engine and exhaust fumes from a passing car, she decides to go rolling through the fresh, clean air of the countryside. But, Daisy's brakes fail and she crashes through a wall into the yard of a jam factory. She then knocks over a big tank of jam. She does not mind the nice aroma of the jam.
It is now BoCo's turn to tell his story. BoCo is helping the workmen to make a brand new tunnel in the hillside by taking away truckfuls of unwanted soil. But, one day, it starts to rain and the earth in BoCo's trucks turn to mud. The trucks did not like it either, bouncing about and sending mud flying all over BoCo. The other engines stare when BoCo returns to the Main Station and after being washed, he ends up as the last one back to the sheds. During the night, it rains heavily and the next morning, while on his way to collect more discarded soil, BoCo runs into a landslide and is covered in thick, brown mud again. Luckily, BoCo isn't hurt, but he does need another hard scrubbing. Later, the Fat Controller sends BoCo to collect some goods from a factory. BoCo slows down to enter the factory siding, but he jumps right off a loose rail and smashes his way through the big, wooden factory doors. Inside, he hits an enormous tub of sticky, brown goo. It splashes all over BoCo's face as he grinds to a halt. At last, a factory crane lifts BoCo back onto the track and he limps home. Just as a guard prepares to give BoCo a good scrubbing, BoCo stops him. BoCo sticks out his tongue and licks some of the goo off his face. The other engines gasp; thinking that the messy diesel had just eaten mud. BoCo laughs and tells them all it is actually chocolate!
Daisy and BoCo laugh at their incidents, saying that it was nothing to worry about. Percy agrees, but Class 40 says that he begs to differ, and tells his story.
Class 40 has come to the yard to help shunt trucks, but he is not happy because the steam engines keep blowing smoke everywhere. He rudely tells the steam engines that they should be scrapped. Thomas and Duck tell Class 40 that they cannot help hissing steam and puffing smoke. The Fat Controller overhears the angry voices and, to avoid an argument breaking out, he gives the Diesel a new job. He is to take some workmen to a nearby factory. As Class 40 arrives at the factory, he sees a very tall chimney puffing out lots of smoke. The Diesel coughs; the tall chimney is even worse than the steam engines. The Diesel's passengers explain that they are to demolish the chimney as it is too dirty. Class 40 tells the other engines about the old chimney, back at the station. He tells them that chimneys and funnels are all the same - no-one wants them. The steam engines fume quietly. A week later, the Diesel is instructed to take some trucks to collect the rubble from the factory. The Diesel arrives at the factory just in time to see the chimney go crashing to the ground. Suddenly, a cloud of dust from the falling brickwork covers the startled diesel, blowing into his eyes and mouth and up his nose. When he returns to the main station, the Diesel looks like a sorry sight. Instead of being shiny and spotless, he is grimy and dusty. Thomas and Duck stare in surprise. The Diesel rolls sulkily past the steam engines to get hosed down. Thomas tells the Diesel to keep away from them; they may be smokey, but they're not as messy as the dusty diesel.
Class 40 says that the accident was terrible, but everyone kept laughing, while the diesel fumed.
- The Blue Tender Engine
- Class 40
- Sir Topham Hatt
- Mavis (cameo)
- Annie and Clarabel (cameo)
- This is based off the three magazine stories, Sweet Scent, Choc-o-BoCo, and Dusty Diesel.
- Whenever the diesels take a turn telling their stories, they blast their horn and transition to the story with their smoke like in Shining Time Station when Mr. Conductor blows his whistle, fading to white, transitioning to his story.