Air date: May 5th, 1992 (UK), December 25th, 1991 (US)
Adapted from: Tramway Engines, "Toby's Tightrope"
Percy arrives at the quarry to pick up stone for his trucks. The only other engine in the quarry at the moment is Mavis who is sheltering between rocks looking miserable. Percy tells the young diesel to cheer up, but she explains that her manager found out about her going down Toby's line and causing trouble and has confined her to the quarry. She calls Toby a fusspot again, angering Percy who tells her that Toby knows a lot about trucks and that they must be left where he wants them. Percy then leaves to take his trucks to the harbour. Although Mavis likes Percy, she still does not understand why she cannot go down the line.
The siding arrangements at the quarry are very awkward and Mavis is forced to make several journeys to put the trucks in the correct place. Mavis is desperate to leave the quarry and makes a plan. She starts by telling her driver the work would be a lot easier if she could use a small part of Toby's line. Her driver, suspecting nothing, agrees and allows her to go as far as the first level crossing.
The weather changes, with the snow and ice melting away. This causes an increase in work and Mavis takes trains that are so long that she has to go beyond the level crossing. She decides to proceed with her plan to go further down the line without making it look like her fault and asks the trucks to bump her at the level crossing. The trucks agree, but things go awry when Toby arrives while she is gone and decides to shunt them himself. The trucks decide to bump Toby instead and when Toby reaches the level crossing the trucks push him down the line.
Melted ice and snow had caused the river on Toby's line to become a torrent and it washes away a crumbling wooden bridge after a log collides with it but leaves the rails behind which form a tightrope across the abyss. Toby's driver fights for control and by the time Toby is finally able to stop, he is on the "tightrope" precariously above the water, ready to fall any second as more pieces of the bridge crumble into the torrent.
When Mavis hears what has happened, she is horrified and immediately goes to help. Toby is anchored to some rocks with chains as Mavis takes away the trucks. Eventually, she is able to pull Toby to safety and later apologises about what happened with the trucks. Toby thanks Mavis, telling her that he does not fancy walking any tightropes again.
The Fat Controller sees Mavis later and congratulates her for doing well in an emergency. Mavis admits she was responsible for the trucks' behaviour but asks if she can still use Toby's line as Toby has offered to show her what to do. The Fat Controller agrees on the condition that Mavis' manager allows her to, which he does. Mavis is now happier than ever and is considered to be a Really Useful Engine.
Tropes featured in the episode:
- Alliterative Title: Toby's Tightrope.
- Big Damn Heroes: Mavis pulling Toby from the decayed bridge.
- Character Development: Mavis is all too eager to leave the quarry and not very fond of Toby. She mellows out when she hears about Toby's plight and rushes over to help him.
- Composite Character: Percy takes the role of Mavis' manager from Tramway Engines in telling Mavis that Toby knows a lot about trucks and that they must be left where he wants them.
- Darker and Edgier: This is an example of one of the rare moments in the show where a character's actions lead to a genuinely serious incident. Even the already frantic-sounding runaway theme has some added stings at its ending to emphasise the danger.
- Digital Destruction: In the restored version, when the trucks yell "On, on, on!", a hand can be seen pushing them along.
- Easily Forgiven: The Fat Controller didn't punish Mavis for the trouble she caused with the trucks and Toby since they were pleased with her rescuing Toby. Of course, she admits that it was her fault. Toby himself is also pretty easy going.
- Jerkass: You would never guess, but the Troublesome Trucks.
- Jerk with a Heart of Gold: Mavis.
- Kick the Dog: The trucks push Toby onto the rickety trestle even though he does nothing to wrong them.
- My God, What Have I Done?: Mavis has one when she asks the trucks to push her down the line she isn't supposed to go on, only for them to push Toby instead.
- No Sympathy: Percy didn't seem quite phased by Mavis' complaints about how she isn't allowed to go through the line and how Toby has been criticizing her in handling the trucks.
- Not-So-Harmless Villain: The trucks push poor Toby and his driver onto a broken wooden bridge, and Mavis has to come to their rescue before the bridge breaks underneath them and sends them falling into the rapid river below.
