Air date: July 15th, 2017 (UK)
It is autumn and Thomas meets Toby along his branch line, who finds the trees look spooky. Thomas moves along and sees a broken fence. He informs Trevor of the fence, who says he will tell Farmer McColl about it.
That night, Thomas tells the other engines about the fence. Percy is nervous as he sets out to pull the mail train. He is making his deliveries and comes across a bridge on the branch line, and all of a sudden, hears a moaning sound. Frightened, he rushes back to the Sheds to tell the others. He runs in so fast, that he rockets right into Henry, who rolls further into his berth. Gordon is not amused nor interested. Percy, however, is very apprehensive toward the sound he heard.
The next morning, Percy tells Toby and Thomas about it. Thomas assures him there is probably nothing to worry about. Toby, on the other hand, is baffled and scared by this, and is not looking forward to crossing the bridge on the way to the Quarry.
Later, Thomas is nearing the bridge and decelerates, puzzling Annie and Clarabel. Thomas tells them what he is up to, but suddenly hears the moaning sound Percy told him about, hollers, and dashes away.
Thomas, Percy and Toby meet up at Ffarquhar and discuss the sound they heard. Percy, remembering the story of The Three Billy Goats Gruff, thinks it is a troll. Toby agrees, reminding the others about how the littlest goat survived by going across the bridge first and telling the troll to eat his bigger brothers. The engines are all very scared and do not want to be consumed by the "troll".
Toby claims first, and Percy second, leaving Thomas to go third. At the bridge, Toby, Henrietta and Percy hurridly cross, leaving Thomas on the other side. Slowly proceeding across, Thomas, Annie and Clarabel hear the noise and listen more carefully, and realise it is a cow mooing. Toby and Percy are surprised too, and they fetch Jem Cole, Farmer McColl and Trevor to rescue the cow, who had escaped from the broken fence. Thomas takes her back to Farmer McColl's farm.
That night, Thomas, Percy and Toby tell the other engines about their adventure. Edward, Henry, Gordon and James laugh, but Toby and Percy are agitated and say it is not that funny. Thomas, not having any hard feelings, says it was a little "a-moosing."
This episode contains examples of:
- Character Check: Reversed. While the recent episodes had mostly reverted Toby back to his original characterisation, here is full-on back to his Hit-era Lovable Coward persona.
- Dirty Coward: Discussed. Toby recollects how the Three Billy Goats Gruff sent the youngest goat first over the bridge, with each one convincing the troll to eat their bigger brother instead. Fearing being sold out, Toby and Percy rush to the front.
- The Bus Came Back: Trevor gets his first speaking role since Season 9's "Henry and the Flagpole".
- Pun: In the ending, Thomas mentions that the adventure was "a-moosing".
- Shout-Out: The episode is based around the fairy tale of The Three Billy Goats Gruff; the story is also mentioned in the episode by Percy and Toby.
