On some old sidings out of the way, Diesel 10 had used his claw to carve his face into a mountain. "Beautiful; I could cry," he muttered to himself.

"Uh, Boss-"

"Now we're here?"

When Diesel 10 wasn't looking, two more diesels had rolled alongside. They were smaller than him, but they still didn't look friendly. Diesel 10 coughed and spluttered. "A-Alright, listen, you two. I, er, I've got a job for you, Splodge."

"Actually, it's, er, Splatter," said one of the diesels.

"And-and Dodge," said the other.

"I don't have time to say both names!" Diesel 10 growled. The two small diesels looked at their buffers. "While the Boss-"

"Isn't that you?" Splatter cut in.

"The other one, Fat Hatt! While he is away, the cats, that's us, will play…and we'll catch our mice." The two diesels said nothing. Diesel 10 groaned. "We're going to make life a misery for those steaming heaps of trash on wheels. This Island doesn't need them; it needs diesels! There's no use for steam engines these days; they're history! I've also come back to find a steam engine."

The twins twittered together.

"Oh, that's easy."

"Yeah, they're everywhere."

"Yeah."

"Not the one I want," said Diesel 10. "She's special. As long as she exists, so do the others, but if she can be destroyed-"

Dodge and Splatter were shocked.

"D-Destroyed? Did you say destroyed?"

"The 'D' word?"

"Like 'hurt'?"

"Yes, destroyed," Diesel 10 frowned.

Now, Splatter and Dodge felt even less sure of themselves.

"Er, there's one small problem. Er-"

"Yeah, Mr. Collett's coming, and he won't let you destroy."

"He won't let you."

"No."

"I can do whatever I want!" Diesel 10 shouted back. "I'll get him too…with this!" He raised his claw high and clashed it. Suddenly, it fell and bashed him above his face. "Ow!" he cried.

The twins chuckled.

"I don't think he meant to do that."

"No."

Diesel 10 grunted. "Those blasted engineers. They've got to get the bugs out of this thing."

Later, Thomas arrived at Knapford Station. Mr. Collett went to Sir Topham Hatt's Office. No one was there, but he found a note on the desk.

Dear Mr. Collett,

Where were you? My wife said she couldn't miss our little holiday.

Will telephone to make sure you have arrived.

- Sir Topham Hatt

Sure enough, after a few minutes, the telephone rang. Mr. Collett received his orders and went about his work. Later, he was out on the platform when he heard a voice.

"You're Alexander Collett." Mr. Collett turned to see an older man in grimy black clothes. "You know who I am?"

Mr. Collett frowned. "You're P.T. Boomer. I heard you left this Railway a long time ago."

"Well, now I'm back. I'm looking for Burnett Stone. Where is he?"

"Wherever he wants to be."

The man smirked deviously. "You can't fool me, Collett. I'll find him."

"There are good people around here, Boomer. Don't mess with them." Boomer just grunted as he turned and walked away…knocking over a luggage trolley as he went.

Mr. Collett sighed; he had heard stories about P.T. Boomer. Long ago, he used to work on the Railway. Then, something happened between him and a Driver called Burnett Stone, and he disappeared after that.

Mr. Collett tried not to worry. He helped recover the luggage and went back to Sir Topham Hatt's Office. He didn't notice Diesel 10 slinking through the Station, and he had heard everything.

Meanwhile, the other engines were confident, cheerful and determined not to be bullied by Diesel 10. Only James, who now felt Really Useful too, was complaining. "Wobbly wheels!" he grumbled.

Nearby, Thomas was collecting trucks. "You're just jealous, James."

"Puffy pistons! You shouldn't have collected Mr. Collett. I should have."

Gordon stopped alongside. "James is right, little Thomas," he said proudly. "Collecting people like Mr. Collett is an important job. 'Important' is 'big' and we are big engines. You are small, so we should've picked him up."

"Bossy sprockets!" fumed Thomas. "All that steam has gone to your funnel." And he bumped his trucks hard.

"Stop squabbling, all of you," said Toby the Tram Engine. "What's important is to stand up on up our own wheels to Diesel 10."

What none of the engines noticed was Splatter and Dodge sneaking into the Yard.

"Hey, there they are."

"We'll fix their wagons."

"I'm not good at backing up."

"Me neither."

"I think Diesel 10 believes the legend of the Lost Engine," said Henry the Big Green Engine.

"What legend?" asked Percy the Small Engine.

"Of one of the oldest engines on the Island of Sodor," Henry explained. "A long time ago, some of the older engines on this railway were sent away, but some say that one of them didn't leave with the others and that she is still on this Island somewhere. Diesel 10 believes that if he can destroy her, he can get rid of us as well. That's why he wants to find her."

"Then we'd better find her first," Percy wheeshed.

"Leave it to the big engines, Percy," grinned James as he puffed away.

"Hmm, little engines can do big things," said Thomas, "especially when they have nice blue paint like me."

In a corner of the Yard, Splatter and Dodge were chuckling.

"Hey, hey, just watch what happens to that blue puffball."

"When Harold the Flopper Chopper flies past here."

"Right."

Sure enough, Harold the Helicopter approached from above. "Routine flyby, chaps, hullo!" he called.

The two diesels watched with interest. They knew about Diesel 10 sneaking through the sidings earlier.

"The Boss dumped sneezing powder everywhere."

"Let's start laughing now." And they did.

Sure enough, as Harold swooped overhead, large clouds of dust blew everywhere. Thomas was covered from top to tracks.

As for Splatter and Dodge, their laughing soon turned to coughing as they were covered in dust too.

"Er, did you mean to look like that?"

"Er, no."

"Er, neither did I."

"Ooh, sorry, troops!" Harold called again. "A bit of a dust-up! Love to stay and clean up! Got to go! Bye now!"

Thomas puffed away, sneezing. "This must be Diesel 10's doing."

That evening, Mr. Collett climbed aboard Bertie the Bus and made his way to Tidmouth Sheds where the engines were settling down for the night. "Good evening, everyone."

"Good evening, Sir," said the engines.

"Now, Sir Topham Hatt expects this Railway to run like clockwork. You all must get a good night's sleep. It's going to be another hard day tomorrow and you all must be responsible, reliable and Really Useful."

But no one noticed that Diesel 10 was hiding in the shadows. He was on a siding next to the Sheds close to some scaffolding. The Sheds were being repaired too; lots of bricks needed replacing.

Diesel 10 waited for just the right moment. Then…CRASH! The scaffolding came crashing down, shaking the Sheds, making everyone jump and sending dust flying everywhere.

"Cinders and ashes!" cried Thomas. "It's Diesel 10!" All the engines looked on in fright.

Diesel 10 cackled as he rolled forward, clashing his claw. "Hullo, Mr. Collar. Okay, greetings' over. Now, where is that Lost Engine?"

Mr. Collett stood his ground. "You won't find her here," he said firmly.

"You're not clever enough to stop me."

"Oh yes, I am."

"No, you're not!" Thinking quickly, Mr. Collett reached into his pocket and pulled out a bag for his evening tea. Diesel 10 jumped. "Is that-?!"

"That's right, it's sugar, Diesel 10, and if I throw this in your tank, it'll seize you up for good!" The big diesel shuttered in fear. "Now, be off with you and if you try anything else again, I'll inform your owner and make sure they have your claw removed."

Diesel 10 rumbled across the turntable. "Make the most of tonight, Crier," he grumbled, "because you won't like tomorrow! Neither will that…that line of tin kettles!" And he disappeared into the darkness.

"Oh, Mr. Collett, what are we going to do?" moaned Percy. "What if that diesel causes more trouble? He's so scary."

"Don't worry, Percy. We'll talk more about this in the morning. You just go to sleep now." And he left.

"…Easy for you to say," said Percy quietly.

Mr. Collett and the engines had no way of knowing that on another part of the Island, there was someone else who could help. Burnett Stone, now an old man, used to be one of the best Drivers on the Railway. He also knew the legend of the Lost Engine better than anyone and heard about Diesel 10's return. That night, he pondered the situation once more. "…If you can survive…then so will everything that makes this Island special."