'Arry and Bert are some of the most troublesome engines on the Island of Sodor. Sometimes, it can be very hard to keep them in order. They like playing tricks on steam engines and believe they are better than them at everything, but they quickly learned that playing tricks on certain engines, like Edward and Duck, was a mistake.

One day, the Fat Controller came to Tidmouth Sheds. "Nia, I want you to collect some trucks from the Smelter's Yard and take them to Vicarstown."

"Yes, Sir," replied Nia.

Percy was worried. "Watch out for 'Arry and Bert," he said. "They like to cause trouble."

"I will, Percy." And Nia puffed away.

Soon, Nia arrived at the Smelter's, and saw 'Arry resting in a siding. "'ello," he said, "haven't seen you around here before."

"I'm Nia. I've come to collect some trucks for Vicarstown."

"On that siding over there."

"Thank you."

As Nia puffed off, Bert rolled up alongside. "Well, well, another tank engine to tease. She seems a simple sort of engine."

"Are you thinking what I'm thinking?" said 'Arry slyly. Bert sniggered back.

Nia made her way into the sidings and backed up to her trucks. Then, it happened. Nia looked ahead and saw 'Arry shunting some trucks in front of her. "Wait! What are you doing?" she called, but it was no good; the trucks bumped into her.

"Lil' orange piggy in the middle!" teased 'Arry, and he rolled back.

"What is going on?!"

"Those trucks need to go to Vicarstown too," jeered Bert. "You better hurry or you'll be late."

Nia, her Driver, and her Fireman all sighed. There was no time to shunt the trucks themselves, so Nia set off slowly, trucks in front and trucks behind. Usually, Nia doesn't mind being a middle engine, but this was unexpected and unplanned.

At last, Nia arrived at Vicarstown Yard where Rosie was waiting. "I'm sorry I'm late," said Nia sadly.

Rosie looked at Nia's predicament. "Let me guess; 'Arry and Bert."

"Yes."

"Those diesels are always causing trouble for us," sighed Rosie. "They say, 'steam engines are no good' and will use any excuse to push us around."

"Well, I've been thinking, and I say we can be just as clever as they are." And Nia explained her plan to Rosie.

First, Nia asked the Fat Controller if more trucks needed collecting from the Smelter's Yard in the morning and volunteered to collect them. The Fat Controller was surprised, but agreed.

Then, late that night, Rosie volunteered to take some empty flatbeds to the Smelter's. 'Arry and Bert were asleep, so she puffed along carefully. She shunted the flatbeds where they were needed and raced over to a line of full trucks. Rosie was coupled up and moved them onto a long siding that disappeared around a bend, stopping behind a work shed so only the trucks could be seen.

The next morning, Nia, arrived back at the Smelter when 'Arry rolled up. "'ello, Nia," he said greasily. "Back for more trucks?"

"Yes," replied Nia. "Where are they?"

"Over there."

Nia could see a small line of trucks arranged on the long siding where Rosie was hiding. "Thank you," she said, and sniggered as she puffed away; her plan working. Rosie had her brakes on and made 'Arry and Bert think the siding was full, but the diesels managed to arrange the trucks just as they wanted. As Nia backed up to them, Rosie heard her and smiled. It was time to play their own little trick.

Sure enough, Nia saw Bert rolling toward her with more trucks. "Now!" she shouted. Quickly, Rose pulled the trucks away as Nia shunted them backwards. 'Arry and Bert were surprised. Nia passed a set of points and her Fireman quickly jumped down and switched them. Bert applied his brakes and stopped quickly, almost crashing through some buffers.

Nia chuckled as 'Arry and Bert stared. "What…How…?" they spluttered.

Rosie puffed out from behind the trucks. The diesels were speechless. "It seems you're not the only clever engines around here," teased Nia.

"Quite right," said a well-known voice. It was the Fat Controller. "It's a good thing I was visiting this Yard today." He looked sternly at 'Arry and Bert. "The Yard Master at Vicarstown told me about what happened yesterday. You both made Nia late and nearly caused confusion. You never know when to stop, do you? For your punishment, you will deliver your own trucks until I can trust you again."

After the Fat Controller left, 'Arry and Bert looked very sad. "We're sorry, Nia," said 'Arry.

"We promise we won't tease you again," added Bert.

Nia smiled; she could tell the two diesels were sorry. "Thank you," she said. 'Arry and Bert quickly rearranged the trucks, and it wasn't long before Nia and Rosie were traveling back to Vicarstown together.

Soon, 'Arry and Bert went back to shunting in the Yards again. They still like playing tricks on steam engines, but ever since that day, they have both earned a new respect for Nia and Rosie.