One day, the trucks push Henry off the rails, breaking his wheel. Henry will have to be sent to the works, but he does not mind much; at least he will be away from the mischievous trucks. The Fat Controller rushes to the scene of the accident and tells Henry that Diesel can do his jobs while the big engine is being repaired. He goes on to warn the trucks that Diesel is not used to heavy loads and to be behave with him.
Diesel is not worried; he thinks he can pull more trucks than the steam engines. The troublesome trucks sense a chance for frolics. When Diesel has shunted a long line of trucks, he pulls and pulls but cannot move the heavy wagons; they had slipped their brakes on. The trucks tease Diesel and encourage him to pull harder. Diesel does so and the coupling snaps. Diesel shoots forwards and falls right over the edge of the docks.
The Fat Controller is not impressed and is glad to see Henry return to work. Henry backs up to the trucks, checks that the brakes are off, and then pulls away with a cheerful toot. Everyone cheers and even the trucks are well behaved for the rest of the day. The other engines were happy and had learned a valuable lesson; even trucks can do the engines favours sometimes - like getting rid of smelly Diesels.
- It is said that the Fat Controller is at the scene of Henry's accident, but the image used shows him inside Tidmouth Sheds.