Thomas the No. 1 is the fourth volume of the New Railway Series.
Thomas is collecting some lemons for the Vicar of Wellsworth when Percy accidently sqeezes the lemons all over Thomas! Thomas is cross with Percy, but gets even crosser when the engines and Trevor make fun of him.
Thomas has a piece of egg shell in his whistle, so he must be repaired. A little boy starts Thomas up though, and Thomas soon becomes a runaway. He races through Crovan's Gate where Rosie and Duke are waiting. It's up to Rosie to save Thomas.
When the Fat Controller tells Thomas to take the Brass Band, Thomas tries to avoid Percy, being cross since he thought that Percy was the one that caused his bad-luck chain. Duck, Neville, and Percy are confused until Thomas reveals his thoughts to Duck.
Thomas and James get worried that a big balloon will replace them. Things get worse when Percy accidently pops it.