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“How come I didn't see the invisible engine?"
"Probably because he's invisible, eh?”
―Percy and Nia

Seeing is Believing is the thirteenth episode of the twenty-second series.


Merlin is visiting Sodor from the Mainland to deliver steel. He is excited about visiting Sodor as he will be seeing Thomas and tries to make himself invisible, to which Thomas jokes about not being able to see him. Salty later jokes about this to Rebecca, though she finds out that he is not actually invisible.

Merlin later comes up alongside Thomas and surprises him. While doing so, Merlin hears a whistle in the distance and is surprised by Trevor, having never seen a traction engine before. Thomas then introduces Trevor to Merlin, who also tries to convince Trevor about his invisibility.

All of the engines at Tidmouth Sheds begin talking about Merlin, though Percy is upset about not being able to see him. He dreams about trying to see Merlin, but cannot because he is invisible. Percy tries looking for him the next day and soon hears a whistle that he believes is Merlin's. Although Merlin comes up beside Percy, Percy does not know that he is the engine and rushes off to tell Thomas about how he has heard his whistle. This makes Percy very happy by how he thinks he has seen the invisible engine.



Voice cast



  • Joseph May as Thomas
  • Kerry Shale as Gordon
  • Rob Rackstraw as James
  • Christopher Ragland as Percy and Trevor
  • Jules de Jongh as Emily
  • Hugh Bonneville as Merlin
  • Yvonne Grundy as Nia
  • Rachael Miller as Rebecca
  • Keith Wickham as Salty
  • Teresa Gallagher as Annie and Clarabel
  • Glenn Wrage as Cranky
  • Lucy Montgomery as Carly
  • Nigel Pilkington as Merlin in Percy's fantasy (uncredited)


  • This is the last episode written by Andrew Brenner, the next series being his last as head writer despite not writing any episodes. David Stoten would take over as head writer beginning with the twenty-third series special episode, Steam Team to the Rescue.
  • This episode marks Merlin's first appearance since Journey Beyond Sodor and his first full appearance in an episode.
  • Trevor uses Vinnie's whistle sound in this episode. This also marks his only speaking role in the twenty-second series.
  • At the beginning of the Latin American Spanish and Brazilian Portuguese version, stock footage from the twenty-second series episode Forever and Ever is used.


  • When Thomas is talking to Rebecca at the docks, some wooden planks are clipping through Carly's rails.
  • Nigel Pilkington was not credited for voicing Merlin in Percy's fantasy scene in the US dub.

Home Media Releases


In Other Languages

Language Title
Brazilian Portuguese Ver Para Crer
Czech Vidět znamená věřit
Danish Man tror det, når man ser det
Dutch Ik Geloof het Pas als ik het Zie
Finnish Uskoo, kun näkee
German Alles nur Einbildung
Hebrew לראות כדי להאמין
Hungarian Hiszem, ha látom
Japanese みえないきかんしゃマーリン
Norwegian Jeg tror det ikke før jeg får se det
Polish Uwierzę, gdy zobaczę
Russian Невидимка
Spanish Ver es Creer (LA)
Ver para Creer (SPN)
Swedish Man måste se det för att tro det


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