For as long as anyone can remember, the Island of Sodor has been the realm of enchantment, innocence, and talking trains. But Sodor's steam engines suddenly find themselves headed for a load of trouble courtesy of the wicked Diesel #10, a train with a plan to dominate the other engines by finding and crushing their dwindling supply of magical gold dust.

Lily (Mara Wilson) has a hunch that her grandfather (Peter Fonda) holds the key to rescuing the little trains in his workshop on Muffle Mountain. Teaming up with Mr. Conductor (Alec Baldwin), Lily sets out to get the Island of Sodor back on track in this beloved, feature-length adventure starring the world's favorite tank engine.