Thomas the Tank Engine's adventure begins when he meets the Flying Scotsman, voiced by Rufus Jones, who happens to be Gordon the Big Engine's brother. The Flying Scotsman is preparing for an exciting competition at the Great Railway Show, where he encourages Thomas to enter as well. However, Thomas feels anxious about his chances of being selected, especially since all the engines on the Island of Sodor are eager to participate.
Determined to impress, Thomas contemplates various ideas to convince Sir Topham Hatt to choose him. His first attempt involves becoming a streamliner; however, much to his disappointment, Sir Topham decides to choose Gordon for this task instead. Undeterred, Thomas then suggests being repainted for the contest titled "best decorated engine." Sir Topham Hatt, again, shifts this idea to James and Emily, leaving Thomas feeling overlooked.
At Brendam Docks, the situation intensifies when Thomas encounters a group of competitors for the Great Railway Show. An unfortunate mix-up with the rail ferry leads to Ashima, a beautiful and decorated tank engine from India, accidentally bumping into Thomas as she rushes to board, nearly sending him into the water. Captivated by her charm, Thomas quickly departs, but soon finds himself filled with jealousy as he watches Ashima step into the role he abandoned.
Meanwhile, Diesel concocts a cunning plan to outsmart Sir Topham Hatt by disguising Paxton, Den, and Dart as trucks, aiming to trick him into entering Diesel into the shunting competition instead of Henry. Ashima, noticing Thomas's struggles, encourages him to embrace his authenticity and consider participating in the shunting competition. Trying to practice shunting by moving Diesel’s train, Thomas inadvertently causes a crash, resulting in consequences.
Sir Topham Hatt reveals that he had always intended to select Thomas for the shunting challenge. However, due to the necessary repairs, Percy the Small Engine is called to take his place. In a twist of fate, Thomas hurries toward the competition after learning that Gordon's safety valve hasn’t been properly installed, leaving him vulnerable.
At the Great Railway Show, things take a disastrous turn for the representatives from Sodor—Henry, James, and Emily all face losses in their respective competitions. The situation worsens for Gordon, who is eliminated from the race after his boiler unexpectedly explodes. Encouraged by Percy's enthusiasm, Thomas reclaims his position in the shunting competition. In a selfless act, he sacrifices his own victory to help Ashima avoid a collision with a derailed flatbed. Graciously, the judges recognize their sportsmanship and award them both a tie.
As the Railway Show concludes, Thomas invites Ashima to visit Sodor with him, allowing them a chance to spend some quality time together before she catches her ship back to India. However, Diesel's unanticipated misfortune has him mistakenly loaded onto a ship departing Sodor, leaving the diesels and Cranky the Crane to watch in disbelief as he sails away from the island.
