

When Salty the Diesel Engine returns from his worldly travels, he sings a shanty to Thomas and Percy about a legendary treasure lost on the Island of Sodor. The two friends are eager to see if the legend is true, but their journey comes to a snag when the rest of the Biggest Adventure Club refuses to join.
On their way to a celebration for Thomas' 10,000th delivery, Percy tries to help Thomas with his big speech, but Thomas fails to listen. While distracted, Thomas doesn't notice when Percy falls off the track and gets lost. Percy tries unsuccessfully to find his way to familiar terrain.
When Bruno comes along to help Diesel get a heavy load to the Lighthouse, Bruno tries suggesting a safer route, but Diesel doesn't wait long enough to listen to him.