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“Oh dear! I never meant to upset her. What if I've upset her so much that she's run away?”

Runaway Engine is the fifth episode of the twenty-first series.


Millie is given extra work around the estate, so the Earl tells Glynn and Stephen of the jobs they have to do, despite their constant chatter. Millie gets agitated when Stephen forgets to clear up garden waste, so she dumps it in front of his shed in the estate. Rather than an apology, Stephen makes fun of her, hurting her feelings.

By the next day, he tries to apologise to her, but cannot find her, leading him to think that she must have run away. Going out of his way away from the estate to look for Millie, Stephen runs out of water while pulling his passengers.

To Stephen's luck, Millie, with the Earl on board, find him. Millie and the Earl explain that she had gone for a new motor for the estate castle's turntable and that he and Glynn were not listening to his orders yesterday morning. The Earl sorts out the stranded passenger train - soothing an angry passenger - and Millie, Stephen, and Glynn make up again.






  • Going by production order, this is the tenth episode of the twenty-first series.
  • A few references to the seventeenth series episode, The Switch are made, such as when Skarloey asks Millie if she was at the Blue Mountain Quarry to help the narrow gauge engines for the second time.
  • This is the first episode of a few things:
    • Luke's first speaking role since the eighteenth series episode, Duncan the Humbug.
    • Skarloey's first speaking role in a episode since Samson at Your Service.
    • The first episode since the eighteenth series episode, Samson Sent for Scrap in which neither Thomas nor any other member of the Steam Team appear at all. This is also the only episode in the twenty-first series and the final episode that does not feature Thomas in any way.
    • The first episode since the eighteenth series episode, Millie and the Volcano to feature Millie as the main character: this is also the first time since the nineteenth series episode, Snow Place Like Home where a narrow gauge engine appears as the main character.
  • The episode marks all the vehicles who appear in this episode's only appearance in the twenty-first series.
  • This episode's title was also one of the working titles for Blue Mountain Mystery.
  • During the close-up of Mr. Bubbles, he is holding a blue, yellow and red balloon, which represent Millie, Stephen and Glynn respectively. The blue balloon then flies away, symbolising that Millie had gone missing.
  • A picture of Glynn from The Adventure Begins, a promo picture of Stephen and a picture of Ulfstead Castle from King of the Railway can be seen on the brochure that the Grumpy Passenger is holding.
  • This is the fourth and last episode to have the same cast in both English dubs, after Luke's New Friend, The Switch and Blown Away.
  • In the Nick Jr USA airing of the episode, it was paired with Confused Coaches.
  • A shortened version of the episode, narrated by Joseph May as Thomas, can be found on the official YouTube channel and the Nick Jr website.
  • This episode marks Glynn and Millie's last speaking roles until the twenty-third series episode, Heart of Gold.


  • When Stephen and Glynn discover the garden waste, Stephen's shed doors are shut. But when Millie puffs on the turntable, the doors are open.
  • In the overhead shot of Millie backing up to the loading shed at the Blue Mountain Quarry, a narrow gauge train is travelling on standard gauge rails.


In Other Languages

Language Title
Brazilian Portuguese A Locomotiva Fugitiva
Japanese ミリーをさがせ!
Polish Obrażona Lokomotywa
Romanian Locomotivă Scăpată de Sub Control
Spanish Locomotora Fugitiva

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