Episode 24 was uploaded on November 21, 2016 and is the eighth and final episode of the third season. It completes the story from episode 18 and 19.
One morning at Wellsworth, BoCo is getting a passenger train ready when he sees Diesel shunting in the yard. BoCo says good morning to Diesel, who stops, as if about to say something, but doesn't and continues his work. BoCo isn't surprised by his behavior.
Later that afternoon, Diesel approaches BoCo and apologizes to him that he didn't respond to BoCo that morning as no one ever says that to him. BoCo accepts Diesel's apology. Diesel explains to BoCo that he has a reputation(to which he thinks BoCo may have heard it) that he has changed. BoCo says he can see it very well. BoCo then asks Diesel what it was that made Sir Topham Hatt keep him on his railway and as a permanent resident. Diesel says that it's a long story, but thinks BoCo has the right to know.
The scene then cuts to 2002 after Diesel was loaded out of the barge he fell into while trying to pull a line of 20 trucks with their brakes on, and he was heading back home in disgrace. It had been the third time that he messed up on the North Western Railway, and Diesel knew for sure that he was never coming back. As night was approaching, the Class 08 stopped at Crovan's Gate for the night. The news about his mess up soon spread, as the Skarloey Railway engines had scowled at him. Diesel ignored them, sulking as usual.
That night, Diesel had a dream wasn't reassuring; a nightmare which was about his brothers, making it even more unsettling was that it was true.
The next morning, Diesel woke up very late, not having a good night. Gordon had noticed that Diesel hadn't gone back yet and called him a "filthy b*stard". Diesel's driver tried to get Diesel going by telling him that it's almost eleven o'clock.
In the meantime, at the Steamworks, trouble was brewing. The electrical wires were faulty. Suddenly a loud surging noise followed, making Salty wonder what it was. A workman said that they needed to get the electrical wires fixed, and Toad said that he could smell it. Oliver took a sniff and said that it smelt very burnt, and said there must've been a fire, which there was! Before the fire could be extinguished, it ignited a fuel barrel. The workman shouted for the hose, but the fire had already spread to the walls! The fire alarm blarred and everyone ran out. At that time, Diesel came in and saw the burning building, and Oliver, Toad and Salty were about to be engulfed in flames!
Diesel then recounted his nightmare, and then raced into the Steamworks building to save Oliver, Toad and Salty. One of the workmen shouted, "What are you doing?! Are you mad!?". Diesel didn't respond. First, he pulled Oliver and Toad out of the burning building, then pushed Salty out the other end, just in time as the whole building was engulfed in flames and as they reached the tracks.
Diesel got very hot and exhausted by this, when he realized that the workmen were cheering for him! Diesel, Salty, Oliver and Toad were all shocked and didn't know what to say. It was around that time that the firefighters had starting dozing the flames.
Soon after the fire was put out, Sir Topham Hatt arrived and one of the workmen told Sir Topham Hatt what happened. Sir Topham Hatt said that the building what due for renovation and said they should've done it earlier. Toad said it was thanks to Diesel that him, Oliver and Salty were still standing.
Sir Topham Hatt stared at Toad for a while, then his eyes fixated on Diesel, asking the workmen if it was true, to which the workmen replied yes, and explained what Diesel did. Sir Topham Hatt walked over to Diesel, and when he got to him, he almost said something, but didn't and there was a long silence. Eventually Sir Topham Hatt said "Meet me at Vicarstown later and I shall talk with you." Diesel then said "Yes, sir." and with that Sir Topham Hatt walked away. No one knew what to think nor what to say.
A few hours later Diesel rolled into Vicarstown where Sir Topham Hatt was waiting. As he arrived, Diesel tried to hide the fact that he was very nervous. Diesel reluctantly said "...Good...evening...sir?" Sir Topham Hatt said good evening as well as the fact the Diesel failed his three trials on the North Western Railway: Framing Duck, and making a mess of the harbor twice and that his attitude towards steam locomotives had been despicable and that his father would've never let Diesel come back, let alone twice. Sir Topham Hatt told Diesel that his actions that day were heroic, as he wouldn't know any engines who could save others by racing through a burning building. However, it had put Sir Topham Hatt in a difficult moral dilemma, as engines who tell lies and have no respect are sent away, however, those who risk their lives to save others are of tremendous praise. Diesel saw what Sir Topham Hatt meant by it. After another pause, Sir Topham Hatt decided to renew Diesel's trial and gave one final chance. Diesel was nonetheless pleased and apologized for what he did in the past and promised he would be a really useful engine, and Sir Topham Hatt said he'd see if Diesel could keep it. Diesel did redeem himself, getting into a few arguments at first, only to get attention, Diesel was a different engine, staying silent and doing his work without fuss.
The scene shifts back to present day with Diesel explaining to BoCo that Sir Topham Hatt decided to keep him, and put him on shunting duties at Vicarstown, though Diesel did have some mishaps like the year after Sir Topham Hatt decided to keep Diesel, he came up with a scheme to get Fergus sent to the smelters, but despite that, Diesel had changed his attitude. Diesel's brothers were withdrawn, and that made Diesel realize he was obsolete, as well as BoCo, who only has one brother alive today, but tells Diesel that no matter what happens, he's safe on Sodor, the haven of all types of locomotives.
BoCo then asks Diesel why he hasn't heard of this story, to which Diesel suggests that the steam engines don't discuss it, after all of Diesel's negative associations. BoCo tells Diesel that they shouldn't have a negative image of him now.
BoCo then tells Diesel that he has to get going, and reminds Diesel that if he needs any help, to give BoCo a shout and he won't judge him. Diesel thanks BoCo and BoCo leaves to do his work.
Meanwhile, Crovan has been watching in the distance...
- Crovan (does not speak)
- Fergus (does not speak, appears in flashback)
- Rusty (cameo)
- Duncan (cameo)
- Duke (cameo)
- Peter Sam (cameo)
- James (cameo)
- Daisy (cameo)
- Derek (cameo)
- Duck (mentioned)
- Cronk Viaduct
- Crovan's Gate
- Old Steamworks
- The majority of this episode takes place in 2002 after The World's Strongest Engine.
- Events from Thomas and the Search for Fergus/ Fergus Breaks The Rules are shown.
- Music from the movie The Hobbit: The Battle of the Five Armies is used.
- This was originally not intended to be the season finale. Episode 25 and 26 were before several problems occured and they were upgraded to a special.
- The font used in the Youtube Thumbnail is the same font from the Terminator movies.
- As it is the last video of the year, it is the last video to use the 2016 Henry the Green Engine Productions logo.