“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 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.


  • Stephen
  • Glynn
  • Skarloey
  • Luke
  • Millie
  • Sir Robert Norramby
  • The Grumpy Passenger
  • Rheneas (cameo)
  • Sir Handel (cameo)
  • Peter Sam (cameo)
  • Owen (cameo)
  • Mr. Bubbles (cameo)
  • The Teacher (cameo)
  • The Ginger-haired Boy (cameo)
  • The Welsh Bird Watcher (cameo)
  • One of Dowager Hatt's Friends (cameo)


  • The Estate Railway
  • Ulfstead Castle
  • The Dinosaur Park
  • Blue Mountain Quarry
  • Crovan's Gate (mentioned)




  • A few references to the seventeenth season 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 season episode, Duncan the Humbug.
    • The first episode since the eighteenth season episode, Millie and the Volcano to feature Millie as the main character: this is also the first time since the nineteenth season episode, Snow Place Like Home where a narrow gauge engine appears as the main character.
  • This episode marked the last of a few things:
    • The last episode until the twenty-third season episode, Heart of Gold in where Thomas does not appear at all and Millie and Glynn’s appearances.
    • The last episode to have both English dubs to date.
    • The last episode to not involve Kumiko Higa in the voice cast for the Japanese dub.
    • Stephen and Luke’s last speaking roles to date.
    • Rheneas’ last appearance to date.
  • Going by production order, this is the sixth episode of the twenty-first season.
  • 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 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 is 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.


  • When Stephen and Glynn discover the garden waste, Stephen's shed doors is shut. But when Millie puffs on the turntable, the doors are open.


  • TrackMaster - Runaway Stephen

In Other Languages

Language Title
Japanese ミリーをさがせ!
Polish Obrażona Lokomotywa
Romanian Locomotivă Scăpată de Sub Control

Home Media Releases


  • On the Go with Thomas

External Links

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<< Series 20 Series 21 Series 22>>
#01 Springtime for Diesel #07 Hasty Hannah #13 A Shed for Edward
#02 A Most Singular Engine #08 Cranky at the End of the Line #14 The Big Freeze
#03 Dowager Hatt's Busy Day #09 New Crane on the Dock #15 Emily in the Middle
#04 Stuck in Gear #10 Unscheduled Stops #16 Terence Breaks the Ice
#05Runaway Engine #11 Philip's Number #17 Daisy's Perfect Christmas
#06 P.A. Problems #12 The Fastest Red Engine on Sodor #18 Confused Coaches
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