After several days of being shut up in the shed, the Fat Controller visits Gordon, James, and Henry. He tells the three that he hopes they are sorry and have learned they are not as important as they thought. He informs them that there is a new tank engine named Percy and that Edward and Thomas have been running the main line well by themselves. However, he is willing to let them out and return to work on the condition that they be good and do not complain about shunting anymore. All three agree and they quickly resume their duties.
The Fat Controller then speaks to Thomas, Edward, and Percy and as a reward for their hard work, allows them to play on the branch line for a few days. Thomas happily collects Annie and Clarabel while Edward and Percy go and play with trucks in the yard. Edward and Thomas leave and Percy is left alone where he enjoys watching the larger engines go by. He also enjoys being cheeky to them, which makes them very cross.
Later, after doing some more shunting, Percy heads back to the yard, but the points are against him. Percy is so eager to work, he carelessly forgets that Edward had told him to whistle when he got to the signal box so that the signalman would know he was there. Suddenly he sees something that does make him whistle, in panic; Gordon, on the same line, heading towards him full speed with the express. Percy is horrified, but cannot do anything and closes his eyes as Gordon gets closer. Luckily Gordon applies his brakes and stops just in time. However, by now a frightened Percy has begun to move and intending to run away, begins running backwards.
Percy runs straight through Edward's station and is so frightened he runs straight up Gordon's Hill without stopping. After he descends the hill, Percy quickly becomes tired but is unable to stop because his crew had jumped out when they saw Gordon. Finally, a signalman sees that Percy is in trouble and sets the points into a siding, where Percy lands in a big bank of soil. By now, Percy is so tired he does not care where he stops. He is dug out of the soil by some workmen, who offer him some coal and a drink of water to make him feel better.
Gordon arrives and congratulates Percy on starting quickly and stopping a potential accident. Percy apologizes for his previous cheekiness and Gordon pulls Percy out from the bank.
Now friends with Gordon, Percy quickly settles into his new role as station pilot. Although he never loses his penchant for cheekiness, he now knows to always be careful when he goes on the main line.
- Thomas (does not speak)