- "I've found the oldest engine on Sodor. His name is... Hiro!"
- — Thomas
Thomas is taking on water when Spencer rushes past. All of the engines soon have similar experiences and gather at Knapford to figure out what is going on. Halfway through their conversation, Spencer arrives. It turns out that he is staying for the summer to help the Duke and Duchess build their summer house. Needless to say, nobody is pleased with the news, especially when Spencer rushes around with his work, teasing the other engines. That night, all of the engines are tired and cross because they had all been teased by Spencer.
The next morning, at Brendam Docks, Spencer teases Thomas about his size and strength. Thomas has had enough and the other engines agree with him. Spencer then challenges Thomas to a race to take place at dawn the next day. All of the engines gather in the yard to wish Thomas good luck. Thomas and Spencer are coupled to their loads and Edward announces the start of the race.
Spencer and Thomas race across the Island. Spencer draws ahead while Thomas struggles up a hill with his load. Then the inevitable happens - Thomas' brakes fail and he thunders down the hill and along the main line until he races onto a rickety, old track. After stopping, Thomas finds an old, abandoned engine named Hiro. Thomas is amazed and asks Hiro what he is doing there. Hiro tells how he once worked on another island far away and how he was known as the "Master of the Railway." He sailed to Sodor on a big ship. Sodor was nothing like his old home, but he was still very happy. However, as the years went on, he began to show his age and Sodor did not have the necessary parts to repair him. He was hidden to avoid scrap, but the parts never came from his island and he was quietly forgotten. Thomas' immediate reaction is to tell the Fat Controller, but Hiro believes that if the Fat Controller finds out, he will be scrapped. So instead, Thomas promises to not tell the Fat Controller until Hiro can be a Really Useful Engine once again.
After he finds Hiro, Thomas goes to the Sodor Steamworks to have his brakes mended. The Steamworks is a busy, bustling place, with all sorts of work being done. One particular engine lives there, named Victor, a kind and enthusiastic engine. Thomas is soon repaired and then Spencer puffs into the Steamworks. Spencer starts to boast, but Thomas simply congratulates him on his win. Victor scolds Spencer for taking up space and sitting around chattering. Spencer leaves, very cross about having been spoken to in such a manner.
Kevin then drives clumsily over to Thomas and Victor. Victor scolds him for rushing around, while Thomas notices some engine parts on a flatbed. Thomas finishes his day's work and then comes by later to take the parts to Hiro. Victor says it is only taking up space anyway, so Thomas rushes off with it.
As he leaves, he hears Spencer behind him and quickly hides in a siding covered with trees. Spencer rumbles past and does not see Thomas. Thomas drops the parts off at Hiro's hideout and sets for home when he notices that the new summer house is dangerously close to where Hiro is hidden. Thomas knows he promised Hiro that he would look after him, but now he is worried.
That night, all of the engines are at the Shed. Thomas tells them all about his race and is about to mention Hiro when the Fat Controller arrives. The Fat Controller tells them that there is a lot of hard work in the morning, so they need to be up early and he tells Thomas not to rush around with heavy trucks for no reason; he wants Really Useful Engines - not Really Broken Engines, which makes Thomas worry more about Hiro.
The next morning, Thomas is taking machines to Farmer McColl, but he wants to help Hiro. Percy shows up and Thomas tells him everything. He asks Percy to deliver the machines for him while he goes to help Hiro. Percy does so, shunting his mail coaches into a siding in the meantime.
As Thomas heads to Hiro's Hideout, Spencer appears, wondering why Thomas is not working on his Branch Line. Thomas makes up a quick lie about going to the Docks and rushes off. Thomas waits a while before seeing Hiro again. Once there, his driver and his fireman put the new parts on Hiro. Hiro is very grateful and Thomas heads off, only to run into Spencer who chases him. Thomas soon finds Percy down the line, having broken down while delivering the goods to Farmer McColl. Spencer teases them, but Thomas takes no notice and brings Percy to the Steamworks.
At the Steamworks, Thomas and Percy tell Victor all about Hiro. Victor wonders why Thomas does not tell the Fat Controller, but promises to help. He tells them that every day, he will leave some trucks in a siding with parts for Hiro. But that night, the Fat Controller is very cross. Percy's mail coaches have mysteriously vanished and nobody can find them. Thomas promises that he will find them, but he knows this means he won't be able to help Hiro. So as soon as the Fat Controller leaves, Thomas tells the rest of the engines about Hiro.
The next day, Thomas is hard at work but Spencer is not; he is spying on Thomas to see what he is up to. At the same time, Gordon sneaks along and delivers more parts for Hiro. Thomas is beyond grateful and rushes to the Steamworks. There, Percy has been fixed, but the Fat Controller is still cross about the missing mail coaches. Victor tells Thomas he will have something for him later and the two engines rush off.
Thomas takes Percy to see Hiro. Percy is nervous about Hiro at first, but when Hiro complements him, the two become fast friends. Hiro tells them how he misses his friends from home and also jokingly talks about how he finds Gordon's face to be very unusual when he smiles. The two later head back home. As they do so, Spencer watches from the siding, determined to find out what they are up to.
The next day, Thomas and Percy go out to search for the missing mail coaches, under the Fat Controller's orders. Meanwhile, Spencer tries to harass Emily for information, but she tells him to go find out for himself. Spencer is so cross that he does not notice Percy and Thomas passing on the bridge behind him, with Edward coming down the other way.
Hiro, now in a very "patchwork" design, is feeling much better. Hiro mentions that James would be coming tomorrow, Percy comments on how he feels about James, sending Hiro laughing for the first time in years.
The next day, Thomas and Percy head to the quarry to search for the mail coaches. Spencer had secretly followed them there. But before he can do anything, Mavis appears and offers to show him around, but she is really shooing him away from Thomas and Percy while James sneaks away with more parts for Hiro. Spencer ends up under a chute and his funnel gets filled with slate.
Thomas and Percy are later getting coal and Emily is puffing off to give Hiro more parts. Edward and Henry pass with Spencer in tow, bringing him to the Steamworks. While Spencer is being taken care of, Thomas arrived. Kevin starts dropping things, which causes Spencer to wince and shut his eyes. As he does so, Thomas sneaks away with more parts.
But that night, the Fat Controller is furious. The summer house is nowhere near done, Spencer has been wandering around the Island, the mail coaches still have not been found and Thomas is not working on his branch line. All Hiro needs is one more part before he is completed, so the other engines promise to guard Hiro until Percy delivers the last part.
The next morning, Spencer is repaired and up early, searching around to find out what Thomas is up to. Just then, he finds Percy's mail coaches in a siding and whistles loudly believing that Thomas had been hiding them. James and Toby, meanwhile, are guarding Hiro and puff off to protect him by leading Spencer away from his hideout. Spencer races along with James and Toby whistling behind him, just as Thomas arrives in front of Spencer, blocking his way. The Fat Controller scolds Spencer for playing around with Percy's mail coaches and orders him to give them back at once. Spencer is infuriated and vows to make sure Thomas does not get away with it.
Thomas finds Hiro and tells him that Percy is on his way with the final part. The two are excited, until they suddenly hear Spencer's whistle. Thomas encourages Hiro to puff away from Spencer on his own. As the two make their escape, Spencer appears. Hiro speeds past him and Spencer is very surprised, having seen Hiro for the first time. As Hiro struggles on, parts begin to fall off of him. He cries out for Thomas to help, who can only beg him to keep going. Eventually, Hiro knows he cannot go on and comes to a stop. Spencer can hardly contain himself. He tells Thomas that the engine is bound to be scrapped. Suddenly, Gordon rushes by with the Express, challenging Spencer to race him. As Spencer speeds away, Thomas notices a siding where he can hide Hiro. He tells him that everything will be alright, but Hiro feels worse than ever.
Gordon and Spencer race to the station. Spencer is exhausted, having been running around all day. Gordon wins the race and who should step out of the coaches but the Fat Controller and the Duke and Duchess! While they scold Spencer, Thomas arrives, saying he will help Spencer finish the summer house. The Duke and Duchess are pleased, but Spencer's pride is shattered.
Hiro is miserable, knowing that he will soon be sent for scrap. Thomas begs him not to give up, as he knows how to make everything better. That night, Percy apologises to Thomas for hiding his mail coaches so close to Hiro since he was unaware of how far he was. However, Thomas tells the other engines that he will work so hard on the summer house that the Fat Controller will be pleased, hopefully pleased enough to understand Hiro's case and have him restored. Meanwhile, he encourages the other engines to visit him and keep him company. Thomas works very hard and the summer house is almost finished. While Spencer is talking to the Duke and Duchess, Thomas sneaks off to tell Hiro that soon, everything will be alright. He returns just in time to say goodbye. But as Thomas leaves, Spencer knows where Thomas is going and what he is about to do and decides to chase him down. The two engines race to the station. The two soon cross a bridge that goes over marshland, but one part is broken and cannot hold Spencer's weight. As he crosses, it snaps beneath him and he slithers into the mud while Thomas promises to return with help.
Thomas makes it to Knapford Station and the Stationmaster calls the Fat Controller, asking for him to come right away. When he arrives with the Duke and Duchess, Thomas tells him all about Hiro. The Fat Controller is not cross, nor does he want Hiro scrapped; in fact, Hiro is a very famous engine, the "Master of the Railway." He tells Thomas to bring Hiro to the Steamworks at once. Spencer, meanwhile, has to stay where he is, as punishment for disobeying the Duke and Duchess of Boxford's orders not to leave the summer house.
Thomas heads over to Hiro to tell him the wonderful news and the two engines are overjoyed. Thomas and Percy bring him to the Sodor Steamworks the next day. The Fat Controller and Victor promise to have him running like new again. And so, Hiro's restoration begins.
When Hiro is completed, all of the engines are there and they are amazed at how wonderful he looks. Thomas and Hiro quickly leave to find and help Spencer, who had been stranded where he is for some time. Spencer does not even recognize Hiro when he sees him. He is more than shocked when he finds out that the engine rescuing him is an engine he tried to have scrapped.
Rocky gets hooked up to Spencer and as he pulls, Hiro pulls Rocky and Spencer is soon free of the marsh. They then bring him to the Steamworks. After Spencer is repaired, he works with Thomas and Hiro on the summer house. He also apologises for his behaviour. The Duke and Duchess absolutely love their nice new summer house.
That night, Hiro confesses to Thomas that despite everything, he has become very homesick. Understanding, Thomas tells the Fat Controller, who promises to take care of everything. Some time later, a big farewell party is held at the docks in Hiro's honour; the Fat Controller had arranged for him to return to his homeland. The engines whistle at him and he whistles back. Before he leaves, he talks to Thomas and Percy one more time. Thomas hopes to visit Hiro's railway someday and Percy wonders if Hiro would ever return. Thomas promises that Hiro would always have a home on the Island of Sodor and with that, Hiro puffs away to his ship.