Millie is a French narrow gauge tank engine who works on Sir Robert Norramby's estate railway at Ulfstead Castle. She helps out with maintenance duties on the estate, and takes visitors around the park.
While Sir Robert Norramby travelled around the world, Millie was locked up in her shed. When at last the Earl returned to Sodor, Millie was let out of her shed, and she aided the Earl and the standard gauge engines in rebuilding Ulfstead Castle. When the castle was rebuilt and opened to the public, Millie began taking visitors around the castle grounds, working alongside Stephen. (TVS; King of the Railway)
When Luke came to the Castle with a delivery of stone, Millie took him over to where the stone was needed. The two briefly argued over which of their jobs was better, until Luke got the idea of swapping jobs. While Luke took visitors around the Castle and assisted in maintenance work, Millie was kept busy working up at the Blue Mountain Quarry. At first, Millie struggled to get used to quarry work; she was not used to tunnels, hated getting dirty and struggled with a train of slate trucks when she first arrived. However, Millie learned her way around the quarry and loved the experience, but she was glad to return to Ulfstead Castle. (TVS; The Switch)
During the construction of the Dinosaur Park, Millie aided the workmen and the bigger engines. After being teased by Samson and Harvey, Millie became determined to get back at them. To do this, she had the Groundskeeper make a bonfire behind a volcano model, giving off the illusion that the volcano was real and about to erupt. She succeeded in scaring Samson and Harvey, but was reprimanded by the Earl when he found out about her trick. Millie apologized for her behavior, and was allowed to take the Fat Controller and Dowager Hatt around the Dinosaur Park after its completion. Her idea of the volcano smoke was also used by the Earl, who had the volcano model modified to emit smoke. (TVS; Millie and the Volcano)
Personality and Traits
Millie is painted French blue with white lining. Her boiler bands and pipework are brass, her running board, wheel spokes and the top of her cylinders are gold, and the front of her cylinders and front end are red. Her name is painted in cursive on her boiler, and she carries the Ulfstead Castle crest on her cab.