The Percival twins are celebrating their birthday and every year, Duncan takes them on a special birthday ride. Duncan has been washed and polished and has a special birthday flag attached to his cab in preparation for taking the twins on their special ride. Then Mr. Percival arrives and informs Duncan that this year, the twins will be taking a ride in a hot air balloon instead.
Duncan goes to fetch the balloon from the Transfer Yards. Thomas passes by and remarks about how wonderful the balloon looks, but Thomas also feels sorry for Duncan. On his way, Duncan rolls over some bumpy track and shakes the balloon loose. This gives him an idea and Duncan shakes it more and more until the balloon floats into the air.
Mr. Percival is upset when Duncan arrives without the hot air balloon. Then the hot air balloon lands nearby and bursts. Duncan is upset; now the twins will miss their ride because of him. Duncan volunteers to fetch the balloon repairman.
Duncan races to Upland Station, picks up the balloon repairman and huffs back to the balloon. Unfortunately, the balloon repairman does not have enough material to patch up the hole. Duncan offers his birthday flag to patch up the hole. The balloon is repaired just in time and the twins are delighted.
Soon Mr. Percival and the twins are floating high above the Island of Sodor in the balloon. Duncan feels so happy that he thinks his boiler will burst.
- Mr. Percival
- The Balloon Repairman
- The Percival Twins (do not speak)
- Peter Sam (cameo)
- Mrs. Percival (cameo)