Thomas the Tank Engine was continuing on his journey through South America and before long, he found himself in the country of Peru. He soon arrived at a station and a crowd of people clapped and cheered as he arrived.

A diesel honked its horn cheerfully. It was big and red with orange stripes. "You must be Thomas," it said. "Welcome to Peru. My name is Karla."

"Nice to meet you," said Thomas politely.

"You're in for a fantastic journey," said the Stationmaster. "You and Karla are taking these passengers up to Machu Picchu?"

Thomas was puzzled. "Much-I-Pick…what?"

"Machu Picchu," laughed Karla. "It's an old city from long ago high in the mountains. Now, you take the train and I'll push from behind."

"Why? Wouldn't it be easier if we were both at the front?"

"You'll see," grinned Karla.

When everyone was ready, the two engines set off. As the climbed the steep tracks, Thomas was amazed by how beautiful the mountains were. "Wow, Karla, this is amazing."

The diesel smiled. "Well, we don't have many railway tracks here in Peru, but I like to think we make up for it with the spectacular views we give our passengers."

Soon, they passed through a junction where the other track climbed in the other direction. Then, Thomas saw the end of the track. "Are we here already?" he asked.

"No," replied Karla, "this is what I was telling you about. You know that junction we went through? Well, now we go up the other track."

But Thomas was confused as they set off again. "Why do we have to go backwards to climb this hill? Why can't we just keep going?"

"It's called a zig zag," Karla explained. "It allows a railway to climb a steep hill without having a lot of extra tracks. They are also used if hills aren't suitable for climbing in a straight line. Usually, I have to push my coaches up this section, but with you at the other end, it makes my job easier."

"Well, I'm happy to help, but will we be going backwards the rest of the way?"

"No. First, we zigged. Next, we zag."

Sure enough, Thomas and Karla passed through another junction, and they stopped beyond the points before continuing on their journey. "This is amazing," puffed Thomas. "The beautiful mountains, a railway that zig zags back and forth. I've never seen anything like it."

"You don't have these things where you come from?" Karla asked.

"Well, we do have high mountains on Sodor, but the North Western Railway doesn't climb them. The steepest hill we do cross is Gordon's Hill, but we don't change direction to climb it.

It wasn't long before the two engines reached the final junction on the zig zag, but as they crossed the points, Karla's engine began coughing and spluttering. As they stopped, black smoke billowed around Karla. "What was that?"

Karla's Driver checked her engine. "Well, no more work for you today," he said at last.

"But Thomas can't take the train on his own?" Karla protested.

"Not to worry," said her Driver. "Remember what happens with trains that are too long for zig zags?"

"Oh, of course. Thomas," called Karla, "take as many coaches as you can to Machu Picchu and then, come back for the rest."

Thomas didn't like leaving his new friend behind. "But how will I know which way to go?"

"Don't worry. It's a direct journey to the station from here. You won't get lost."

So, Thomas' Fireman uncoupled as many coaches as Thomas could pull and the little tank engine continued on his way. Later, he arrived at the station where more people were waiting to see him.

"Welcome, Thomas," said the Stationmaster, "but where's Karla?" Thomas' Driver explained everything. "I'll send another engine to collect her."

But Thomas had another idea. "No need for that," he said. "I have something else in mind."

Karla was still waiting with the rest of her passengers when she heard Thomas' whistle. "Did you send for help at the station?" she asked.

"Not exactly," Thomas replied. "You're coming with us."

Now, it was Karla's turn to be confused. "But I don't have to go with you, and won't I be too heavy?"

"Of course not. I took most of our passengers already. Besides, we started this journey together and we are going to finish it together." Karla was flattered and she enjoyed the ride as they continued up the hill.

It was tricky for Thomas to pull passengers as well as a big engine, but he managed to get them all to Machu Picchu. Everyone cheered and praised Thomas for his hard work.

"For a little engine, you are very reliable," said Karla.

"Well, I felt bad about leaving you behind," panted Thomas. "Besides, who would tell me more about Peru with our passengers gone?"

Karla laughed. "I suppose that's true." And the two engines looked out at the beautiful mountain range. "Of course, I wouldn't mind hearing more about your home too, like, why is your steepest hill called Gordon's Hill?"

Then, Thomas laughed too, and the engines spent the rest of the day telling each other stories about their homes and their adventures.