James boasts to Thomas that he is the Fat Controller’s favourite engine and that’s why he gets all the best jobs. And when Henry has an accident, James teases him even more, saying that he is now going to the mainland to have a big adventure, delivering Henry’s trucks. So Thomas gets up very early and takes the trucks himself! The Fat Controller doesn’t mind. He is just pleased that the trucks are going to be delivered and promptly reshuffles the jobs to put James to work on Thomas’ branch line. James is not happy about this at all. Unfortunately, delivering the trucks is not as easy as Thomas thought. Thomas doesn’t know the way and manages to get lost on the Mainland. On his travels he meets some experimental engines who look like no engines he has ever seen before, and stumbles into a Steelworks where he is put to work. When Thomas doesn’t come back, James takes the opportunity to head off to the Mainland himself, trying to find him. But Thomas escapes before James gets there and James gets trapped and put to work in the Steelworks. Now it is up to Thomas and the experimental engines to rescue James and prove that friendship is more important than being the favourite.