Thomas finds out that Bertie has lost his trust in the railway's service after it failed to deliver tar to mend the roads two weeks earlier, and resolves to find the source of the problem.
Meanwhile, James is complaining about having to shunt while Percy is at the harbour to which Gordon advises him to pretend to be sick. When Thomas arrives James tells him he is ill, and Thomas offers to take his trucks for him to the Quarry. The trucks, who are cross at James for bumping them, decide to get to take their anger out on Thomas. On the way back from the quarry, the trucks push Thomas over some points and onto a jetty, which floats across a muddy pond and sinks. Thomas finds the unexpected incident humiliating, especially since the day started so well too.
Duck takes the unhurt trucks away and Edward helps Thomas home. Thomas then remembers about the missing tar and informs Edward about it; he recalls a tar tanker was left at Wellsworth and offers to collect it to ensure it reaches Bertie's road. James and Gordon apologise for their trick, and Bertie arrives saying the road is being mended and he has regained his trust in the railway. Gordon and James slowly leave for the shed, but Thomas is still not alone for it so happens that a toad from the pond has stowed away on his valence for company.
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https://www.youtube.com/watch?v=Ps-FuWBnI2U