- "Percy has a good imagination, Thomas, but I think yours is even better."
The Monster Under the Shed is a picture book.
When the Fat Controller closes the railway early due to bad weather, the engines are stuck at the station. While the engines wait to go back to the sheds, Thomas suggests a story to be told. James tells the engines a story.
A long time ago, there was a tank engine was always ready to help. One night, a stationmaster asked him to get a coach that was left behind. The engine went to get it, but when the weather turned bad. he had to sleep in an old shed. Later, he woke up to a noise and when he opened his eyes, he saw fingers reaching for him from under the shed. The engine was chased out of the shed by a monster and was never seen again.
Later that night, Percy wakes up to a clanking noise behind the shed, but it is only James shaking some scrap. Throughout the night, Thomas hears creaking noises near the sheds. As a result, he stays up all night.
The next morning, Thomas is at Brendam with Percy, who had not heard any noises, making Thomas feel foolish for staying up all night. Henry feels bad for Thomas, while James teases him about staying up all night.
That evening, the engines are telling stories again, but Thomas is too tired to listen. He puffs straight to Tidmouth Sheds without stopping.
While the other engines are sleeping, Thomas hears the same noises he had heard the night before. He sees two glowing eyes and thinks they are those of the monster. However, he finds that it is just a hedgehog, who sleeps on Thomas' running board while he talks to Gordon about Percy's imagination.
- James' splasher is not black.
- Part of Henry's splashier is not black.
- Gordon and Henry's track is missing.
- A light was in Thomas' shed but it cannot be seen.
- On the cover a big hole is seen under Thomas without ballast.
- It is said that James was pulling the express, but he only has one coach.
- The stationmaster said to pick up a coach that was left on the other end of the line. If it is the end of the line, there should be a station, sheds, goods yards, etc, but there is only a shed.
- In the illustration of Thomas puffing towards the sheds, his yellow lining is missing from his cab.
- In the first and third illustrations, James is twice the size of Gordon and Henry.
- James' wheels are grey instead of black