- “You're not Mavis and Diesel!"
"I never said we were, did I?"
"I would've noticed if you had.”
- ―Thomas, Toby and Henrietta
Thomas the Quarry Engine is the ninth episode of the eighteenth season.
One day, there is a big order of stone to be taken from Ffarquhar Quarry to Brendam Docks and Thomas and Diesel are sent to collect it. Unfortunately, they are unable to agree which of them is going to be the back engine. Thomas thinks it should not be him because it is his branch line, but Diesel insists having a revolutionary diesel on the branch line is bound to improve it.
Thomas and Diesel are still bickering when they arrive at the quarry. Mavis is not happy; she thinks they should count themselves lucky. Mavis works in the quarry all the time and rarely gets to see the rest of the island. Thomas asks if Mavis would like to be his back engine, but Mavis says there is too much to do at the quarry. Thomas tells her that Diesel can look after things while she is away. Mavis thinks this is a lovely idea, but Diesel does not. He couples up to the back of Mavis' train and tells her that he is going to be her back engine on their trip to the docks. Mavis asks Thomas if he would mind looking after the quarry for a while. Thomas is not particularly happy with idea of staying at the quarry all day. Mavis warns Thomas to watch out for the Troublesome Trucks, but Thomas says he knows all about dealing with trucks.
Thomas sets to work at the quarry. He fills up all the empty trucks and then pushes them into line, but Mavis was right; the trucks at the quarry are extremely troublesome and do not like being moved. Thomas begins to lose patience and hopes that Mavis and Diesel return soon.
Mavis and Diesel have just arrived at the docks. Mavis loves being beside the seaside and thanks Diesel for letting her come with him. Mavis knows she needs to get back to the quarry, but Diesel spots another goods train destined for the shunting yard. Diesel tells Mavis that they could do that job together, too. Mavis reluctantly agrees.
Back at the quarry, Thomas hears an engine approach and assumes that it must be Mavis and Diesel. Unfortunately for Thomas, it is just Toby and Henrietta taking some workmen home for supper. Thomas explains that he needs to get the Troublesome Trucks to the docks and is in need of a back engine. He asks if Toby will help him, but Toby thinks there are too many trucks for him and he has his own job to do anyway. Thomas is upset, but Henrietta tells Thomas to be patient.
At the shunting yard, Mavis and Diesel have delivered the goods train. Mavis tells Diesel that she has had a great time, but she really needs to get back to the quarry. Tricky Diesel spots another goods train that they can take to Vicarstown and persuades Mavis to come with him to deliver that one, too.
Thomas is still waiting at Ffarquhar Quarry and is becoming more and more impatient. He knows that the Fat Controller will be very cross if the trucks do not get to the docks in time. Thomas thinks that pulling the trucks on his own, without a back engine, will impress the Fat Controller so sets off with the heavy train of stone trucks.
When Thomas reaches a hill, the trucks start playing their tricks. They hold Thomas back as he tries to climb the hill. When they reach the summit, they decide to push him instead. Thomas is pushed down the hill at tremendous speed. Neither Thomas nor the brake van are strong enough to stop the surging trucks who push Thomas towards Maron station. Toby is at the platform and Thomas calls out to warn him. Luckily, a quick-thinking signalman is able to switch the points to divert Thomas onto a siding. Thomas hits the buffers hard and some of the trucks come off the rails. Just then, Mavis and Diesel pull up. Mavis is surprised to see Thomas and asks for an explanation. Thomas explains that he decided to take the trucks on his own because they had been taking so long. Diesel acts innocent and says to Thomas that he had told Mavis several times that they needed to return to the quarry. Thomas, Toby, Henrietta and Mavis were not happy with Diesel's lying, but the Fat Controller is very cross with the scene in front of him.
It is not long before the trucks are put back onto the rails. The Fat Controller tells Thomas that even if Mavis and Diesel kept him waiting for a long time, he should never have taken the trucks without a back engine. Thomas apologises and says he was just trying to be useful.
The Fat Controller sends Mavis back to the quarry to do what she does best, but he does realise that every now and again, it is nice for Mavis to see the rest of Sodor. So, later that day, Thomas acts as Mavis' back engine as they deliver another trainload of stone to the docks. When they arrive, Mavis is so happy that she starts singing, and soon everyone at the docks joins in too.
- Sir Topham Hatt
- Stanley (cameo)
- 'Arry and Bert (cameo)
- Big Mickey (cameo)
- Ffarquhar Quarry
- Brendam Docks
- Sodor Shipping Company
- Knapford Yards
- Vicarstown (mentioned)
- Vicarstown Bridge (mentioned)
- Ben Small as Thomas and Toby
- Steven Kynman as Porter
- Kerry Shale as Diesel
- Teresa Gallagher as Mavis
- Keith Wickham as Salty and the Fat Controller
- Maggie Ollerenshaw as Henrietta
- Matt Wilkinson as Cranky
- Martin Sherman as Thomas and Diesel
- William Hope as Toby
- David Menkin as Porter
- Keith Wickham as Salty
- Teresa Gallagher as Mavis
- Maggie Ollerenshaw as Henrietta
- Kerry Shale as Sir Topham Hatt
- Glenn Wrage as Cranky
- For viewers since the episode came on DVD before Signals Crossed aired in the US, this is the first time Henrietta is seen with a face.
- Most television guides misnamed this episode "Thomas and the Quarry Engine," when it aired in the UK.
- The way that the troublesome trucks pushed Thomas down the hill, into Maron yard, onto a siding and then at the buffers is similar to how they did in Thomas and the Trucks.
- Diesel refers to diesel engines as being revolutionary, likely referencing the second season episode, Pop Goes the Diesel.
- The Troublesome Trucks' eighth season theme is used.
- This episode's original Australian air date coincides with the 30th anniversary of the television series.
- Thomas, Porter, Mavis, Salty and Cranky, all sing part of the song I Do Like to Be Beside the Seaside, during the end of the episode.
- After Salty rolls past Mavis and the shot cuts to a close-up of Mavis and Diesel, the ships behind them have changed position and Cranky seems to have moved.
- Toby says he has to take the quarry workers home for their supper, but it is only quarter past eleven.
- When Thomas is considering taking the trucks of rock by himself, either 'Arry or Bert passes by in the background with a train of rocks. A few seconds later, he is coming back the other way with the same train. The same thing happens when Mavis is shunting at the beginning of the episode.
- The positions of some of the derailed trucks behind Thomas change between shots.
- When Thomas and Mavis arrive at the docks, there are no tracks in the siding outside the Brendam warehouse, but there still appears to be buffers at the end of it.
- When Diesel and Thomas arrive at the quarry, Diesel goes on the line beside Thomas, which leads straight into the engine sheds, but in the next scene, he somehow switches tracks and turns around to buffer up to Mavis' train.
- When Diesel buffers up to Mavis' train, he has a brake van coupled up behind him, but when the train reaches Brendam Docks, the brake van disappears.
- At one point in the Mexican version, only one voice can be heard even though two trucks can be seen talking.
- When Thomas is backing on to the train, his driver appears to be asleep.
- In the Japanese version, Porter has Salty's voice during the scene at Brendam Docks.
In Other Languages