Air date: September 12th, 2005 (UK), September 11th, 2005 (US)
During the height of the busy summer season, the Thin Controller purchases a new engine for his railway. Thomas meets the new engine at the Transfer Yards and the new engine reveals himself as Mighty at one end and Mac at the other. Thomas is surprised as he has never seen such an unusual engine before. Just then, the Thin Controller tells Mighty Mac to take holidaymakers to the campsite in the mountains. However, there are many tracks between the passengers and Mighty Mac, who are nervous as they were used to working in the shunting yards. Thomas advises them to look where they want to go and follow the track that will take them there. Mighty sets off, but then Mac takes the lead, thinking his way is quicker. As Mighty Mac fights over who should take the lead, they end up going in all sorts of directions, even going on the turntable. As a result of their leadership battle, they end up back where they started and nowhere near the holidaymakers at all, making Mr. Percival very cross.
Eventually, Mighty Mac sets off with the holidaymakers. However, their feud is far from over as they argue at junctions on which way to go. Mighty pulls one way and then Mac pulls the other. All of this is making an uncomfortable ride for the holidaymakers, and they end up at a dead end. The holidaymakers are cross and Mighty Mac blames each other. This results in an accident, as they push the coach off the rails and into a giant, solid rock at the bottom of the mountain. This triggers a rockslide, and it blocks their path, causing Mighty Mac to realise how silly they have been.
The holidaymakers set to work to get their coach back on the rails and soon it is back on track. Impressed by this, Mighty Mac work together to shift the rocks out of the way and then collect their coach. They see the flag of the campsite high above them, and remembering Thomas' advice, they set off for the campsite. After they bring the holidaymakers to the campsite, Mighty Mac sets off for home, both agreeing that working together makes them a Really Useful Engine.
This episode contains examples of:
- A Head at Each End: Mighty Mac is a Double Fairlie, a double-ended steam engine. Each end — Mighty and Mac — has a distinct face and identity.
- Conjoined Twins: Being a Double Fairlie locomotive, Mighty and Mac are one engine with a smokebox on each end.
- Early-Installment Weirdness: Mighty Mac uses "they" pronouns several times throughout the episode. In later episodes, Mighty Mac only uses "he" pronouns.
- My God, What Have I Done?: Mighty Mac realise how silly they are after their fighting derails their coach and causes a rockslide to block their way.
- Never My Fault: Mighty Mac blames each other for reaching a dead end.
- Sibling Rivalry: Mighty Mac don't cooperate properly and fight over which direction to take their holidaymakers in. It's only after they see the holidaymakers work together to put their coach back on the rails that they decide to start working together.
