Mr. Conductor's supply of magic gold dust, which allows him to travel between Shining Time and Thomas's island, is critically low. Unfortunately, he doesn't know how to get more. Meanwhile, Thomas is fending off attacks by the nasty diesel engines. Getting more gold dust will require help from Mr. C's slacker cousin, his new friend Lily and her morose grandfather, plus the secret engine.
Thomas the Tank Engine searches for gold dust that will allow his magical friend Mr. Conductor to return home, while also helping a girl restore her grandfather's enchanted locomotive.