Trust Thomas is the thirteenth episode ever made in Season 3.
Thomas find out that Bertie has lost his trust in the railway's service after it failed to deliver tar to mend the roads and resolves to get to the source of the problem. Meanwhile, James is complaining about having to shunt when Gordon advises him to pretend to be sick. When Thomas arrives, James tells him he is ill, and Thomas offers to take his trucks. The trucks, who were cross at James for bumping them, decide to get revenge on Thomas. On the way back from the quarry, they push Thomas over some points and onto a jetty, which floats across the pond. Duck rescues the trucks and Edward helps Thomas home. When Thomas tells Edward about the tar, he recalls several wagons were left at Wellsworth and collects them. James and Gordon apologise for their trick, and Bertie arrives to tell Thomas that his road is about to be mended.
- The causeway Thomas puffs across is the one on Toby's old tramway.