The Tall Controller arrived at Whitehaven Sheds looking worried. "What's wrong, Sir?" Marcus asked.

"Laurence was supposed to take some trucks to Kirkby Stephen, but one of his piston rods is broken."

"I'll take them, Sir."

The Tall Controller smiled. "Thank you, Marcus, but this is a big job."

"I can help," whistled Kenneth.

"Very well, but you both must be very careful and be sure to send clear signals to each other."

"We will, Sir," said Marcus. "What will we be carrying?"

"Items for the Museum in Kirkby Stephen," the Tall Controller replied. It's going to be busy today, so you'll have to take the Keswick route.

"You can count on us, Sir."

When Marcus and Kenneth arrived at the Yard, they found a long line of trucks waiting for them. "Look at that!" exclaimed Kenneth. Sitting on a flatbed at the front was something big and metal. It had a very smooth shape and a propeller on its back.

"Well, bust my boiler!" said Marcus. "It's a submarine! I've never seen one travel by rail before."

"That's because it's not a real submarine," said the Yard Master. "It's a model submarine for the children. Real submarines are much too big for railways. Are both of you taking this train for Laurence?"

"Yes, Sir," said the engines.

"Well, be careful, some of these items can break easily."

"Let's pull out," wheeshed Kenneth.

But Marcus was looking thoughtful. "Actually, the Yard Master said we should be careful. One of us should push in case a coupling snaps."

"What a good idea."

Kenneth made his way to the back of the train and when he was ready, the two friends set off for Kirkby Stephen. As they puffed along, they suddenly heard a familiar buzzing…and Hunter flew overhead. Hunter was a small rescue helicopter and like Thomas' friend, Harold, he looked out for anyone in trouble.

"Routine patrol, chaps!" Hunter called down. "Any trouble here?!"

"Everything's fine, Hunter!" Kenneth called back. "We're just making a big delivery together!"

"Understood, carry on!" And Hunter buzzed away.

Later, Marcus had to stop to take on water. "You know," said Kenneth, "Hunter's rotors were very loud. We might need a better way to signal each other."

"No problem," said Marcus, "how about this? One whistle will mean 'no', two will mean 'yes', three will be for going faster, four will mean 'slow down' and five will mean 'stop.'

"That's a good idea."

When they set off again, Marcus decided to practice their new signals. When they reached a long stretch of line, he whistled three times. Kenneth gave two whistles back to say 'yes' and they began to go faster.

Then, when Marcus saw a red signal ahead, he whistled five times. Once more, Kenneth whistled twice, and they brought the heavy train safely to a stop.

Everything was going well…until the engines were stopped by a workman at Penrith Junction. "There's been a landslide east of Penrith," he said. "You'll have to go north to get to Kirby Stephen."

"But then, we'll be late," replied Marcus. "Can't we take the south route along the mountainside?"

"It might be too dangerous."

Suddenly, Kenneth saw Hunter flying by. "Wait! I have an idea." And he whistled and shouted as loudly as he could. "Hunter!"

The small helicopter landed beside the line. "What's the matter, my friends?"

"We have to get to Kirkby Stephen on time, but east route is blocked and there might be trouble on the south route. Do you think you can watch for trouble from above so we can get through safely?"

"Certainly, mate, my pleasure."

And so, it was arranged. Marcus and Kenneth pulled and pushed their heavy load slowly and carefully along the mountainside.

In the air, Hunter watched the tracks for any danger ahead. "All clear!" he shouted.

The engines only had to stop once for some falling rocks, but lucky for them, they were very small. Once they were past the mountainside, Hunter flew back to the landslide to make sure no one else was in trouble.

At Kirkby Stephen, the workmen were waiting for their shipment as Marcus and Kenneth steamed in. "Splendid!" beamed the Museum Curator, "great work, both of you."

"Well, Sir," said Marcus, "we did have some help from Hunter along the way, but thanks to him and our clear signals, we got here safely and on time."

"And I also heard that you helped Laurence from the start. Well done." And as Marcus and Kenneth watched a big crane unload the submarine, they both felt very pleased with themselves.