Duke, Falcon, and Stuart are three engines who live on the Mid Sodor Railway. Duke is wise, but Falcon and Stuart are cheeky and often make fun of "Granpuff", as Duke is affectionately known, until Duke tells them the story of Stanley, who was rough and was punished by being turned into a pumping engine. The three have many adventures together, until their line closes. Falcon and Stuart are purchased and in due course wind up on the Skarloey Railway, but Duke isn't wanted and is sheltered in the Arlesdale shed. Duke, unaware that the current Duke does not know of his existence, goes to sleep...
In the old days of the Mid Sodor Railway, when Sir Handel was blue and named Falcon, the Manager arranged for him to double-head with Duke to learn the mountain road. Falcon ignored Duke's warnings and derailed, hanging dangerously over the edge. Duke held back, and gathered enough strength to pull Falcon back.
You Can't Win!
Duke is old and Stuart jokes he may have to be kept in order. Duke merely laughs, but later his valves begin leaking and Falcon and Stuart come to the rescue. The cavalcade split up at Marthwaite and Stuart takes Falcon's train with Duke coupled in front. Duke and his driver, hearing Stuart's triumphant chortles, make a plan, and on the last hill Duke gives a great effort. At Arlesburgh a boy enquires as to why there were two engines, to which his father replies Stuart needed assistance and so Duke came to help!
The Small Controller, the Thin Clergyman and the Fat Clergyman hear the story of Duke and go looking for him. After a long search the Fat Clergyman stumbles and falls onto Duke's boiler. Duke is apprehensive, but cheers up when he finds the Duke is coming. Duke, to his dismay, is sent to Arlesburgh by lorry, but is happier to discover he is still popular, and Donald carries him to the Skarloey Railway on a lowloader. [via]