Airdate: June 13th, 2017 (UK), July 6th, 2018 (US)
Adapted from: Small Railway Engines, "Useful Railway"
Mike is annoyed that the miniature railway is not being taken seriously, being referred to by passengers as a "toy railway", and becomes even angrier when his track is blocked by some sheep. That night, while he is complaining to Rex and Bert in the shed, Rex tells Mike that the sheep's wool is used to make clothes. The Small Controller arrives and explains that the farmers have asked the railway to take their sheep's wool to market and that, if they do it well, it will show everyone that they are a useful railway. He chooses Rex to take the first train, as Rex claims that taking wool is an easy job.
The next morning, Rex takes some empty trucks and picks up the wool from each of the farms along the line. The wool has been made into bales that can be stacked into the trucks.
Rex insists that the job is easy, but he and his driver forget that the last load belongs to Willie, one of the farmers. Willie often dawdles and is usually late as a result. Because he is in a hurry, he has not tied his wool bales down to his tractor's trailer and does not have time to stop and do so. As he turns a corner, he loses control and the trailer tips over, causing the bales of wool to fall down a hill and onto the tracks. When Willie hears Rex coming, he runs onto an overhead bridge and tries to slow him down, but he does not realize the line is blocked until after he has passed under the bridge. He hits the wool, derailing him and several of his trucks. The Small Controller arrives to see what has happened. Willie apologises to Rex and the Small Controller for his carelessness and helps reload Rex's trucks.
Bert arrives and teases Rex while he takes Rex's train. Rex remains derailed on the bank for hours, being teased by Mike and Bert when they pass the crash site. Eventually that evening, Mike and Bert come to take Rex home.
When they arrive at Arlesburgh, the Small Controller expresses how proud he is of his engines: Rex for managing to stop and preventing a serious accident, and Mike and Bert for handling on their own in Rex's absence. He tells the three engines that the passengers all admire how they manage and have promised the railway plenty more business.
This episode contains examples of:
- Adaptation Expansion: It's never specified who tried to warn Willie that his load was slipping in the original book, but here, the role is giving to a cycling clergyman.
- Everyone Laughs Ending
- The Freelance Shame Squad: Mike and Bert tease Rex about his incident with the wool trucks.
- Overcrank: Rex when he derails, complete with plenty of Slow "NO!"s.
- So Proud of You: The Small Controller tells the three engines how proud he is of them for each of their actions - Rex preventing a serious accident, and Mike and Bert for taking care of the his duties.
