All the construction work at the big harbour has finished and Percy loves working there. Percy enjoys watching all the different boats in the harbour. There is a lot of work to keep Percy busy in the harbour yard. He spends the day shunting trucks back and forth to the ships. Percy's driver says there is too much work for them to do by themselves and that the Fat Controller will have to get more engines to work the yard. Sometimes, the Fat Controller sends Duck to help Percy in the harbour yard. They spend the night in a special shed where they talk all about trucks and ships.
One morning, the Fat Controller promises that another engine will be arriving to help Percy and Duck in the harbour yard. Percy and Duck wait eagerly for the new engine to arrive and receive a very nasty shock when he finally does arrive. Diesel rolls into the yard, looking as mean as ever. Diesel explains that he is there to help shunt the trucks. Percy and Duck are outraged as they do not like Diesel at all; he had told lies about them before. They refuse to work and will not leave the shed.
The Fat Controller hears there is trouble in the harbour yard and Edward takes him there immediately. When he arrives, the Fat Controller sees Diesel working hard, but Duck and Percy are nowhere to be seen. The Fat Controller then finds them sulking in the shed. Percy tells the controller that they are on strike. Duck explains that they will not work with Diesel. The Fat Controller is not happy and says he is giving Diesel a second chance and the only engines that will be sent packing will be Percy and Duck unless they start working again. Reluctantly, Percy and Duck go to work with Diesel, but they do not like it.
- This story, along with the second part of this story, were adapted for the third season episode, Diesel Does it Again.
- There is a butterfly hidden in every illustration of this story.
- In the ninth illustration, Duck's wheels are green and in the tenth illustration, they are white.
- Duck's handrails are gold.