Spencer has a very important job to do; he is to take the Duke and Duchess to Callan Castle for Lord Callan's birthday ball. As Spencer pulls into Knapford Station, he meets Thomas and Bertie who are arguing about how many wheels are best. Bertie is sure his four wheels are best, but Thomas is certain that six wheels are better. Spencer thinks they are both talking nonsense; his twenty wheels are surely best. Then, Spencer puffs away.
It's not long before Spencer breaks down. Luckily, Thomas is close behind and offers to take the Duke and Duchess to the party instead. Thomas cheekily reminds Spencer that his six wheels are the best as he sets off.
A little while later, Thomas has to stop for a tree that has fallen across his line. Thomas cannot take the Duke and Duchess any further. Suddenly, Bertie pulls up and offers to take the Duke and Duchess to the castle by road. Bertie cheekily tells Thomas that his four wheels have come to the rescue.
There is more trouble when Bertie's driver notices that the bus has a flat tyre. Now he has to stop, too. Bertie's driver radioes through to the Sodor Search and Rescue Centre and soon Harold arrives to collect the Duke and Duchess.
Harold soars over the tree-tops and reaches the castle in no time at all. The Duke and Duchess are very grateful. Thomas, Spencer and Bertie have to agree that Harold had saved the day and he hadn't used any wheels at all.
- The Duke of Boxford
- The Duchess of Boxford (does not speak)
- Annie and Clarabel (cameo)
- Lord Callan (mentioned)