It was a lovely day on The Island Of Sodor. The trains were all on time, there had been no complaints, and even the trucks didn't play tricks. Still, The Fat Controller, Sir Topham Hatt was worried. He knew that the workload for goods had increased dramatically. On Thomas' Branch Line, Percy and Toby were finding it hard to manage the goods all by themselves. Sir TopHam Hatt understood and came to give the two some news.

"Percy and Toby, you have done well to handle the goods, but you need help. A new engine will be arriving in a few days." Percy and Toby were delighted.

"What's the new engine's name?" Percy asked.

"Her name is Mavis, a BR Class 04 diesel." "A diesel?" questioned Percy.

"Don't worry, the owner has assured me she is very kind."

Percy was reassured, but still felt rather nervous. He had a right to be. Sodor hadn't had a good history with diesels. The first diesel, simply named Diesel, was a manipulator who framed Duck and turned the other engines against him; then he did the same to Henry, until Sir TopHam Hatt found out and sent him packing. However, Sir Topham Hatt decided to give Diesel another chance when the work at the harbor had become too much for Percy and Duck. He brought Diesel back a few weeks ago. He caused all sorts of problems and made a mess of the harbor, causing The Fat Controller to send him packing a second time.

Since then, Sir Topham Hatt was very skeptical of ordering new diesels. He bought one named Daisy, a diesel railcar, for a spare engine after Thomas accident when he crashed into the stationmaster's house due to a careless cleaner fiddling with the controls. Daisy was lazy and stubborn and would only do the work she wanted to do, and no more. She also was very boastful about her design and looked down on those inferior to her, specifically the coaches Annie, Clarabel, and Henrietta. After Percy had an accident with some trucks, however, she worked hard to help clean up the mess and to try to run the branch line with Toby. The Fat Controller scolded her for her actions.

"My engines work hard; I send lazy engines away!" he told her.

Since then Daisy has matured a lot, became friends with Thomas, Percy, and Toby, and was a hard worker. Still, her boastful side was still in her, and while she no longer used it to avoid jobs she didn't want to do, it could still annoy the other engines.

So, it was very understandable as to why Percy was so skeptical about the new arrival. On the other hand, it had been shown that not all diesels were bad. BoCo had been a great friend to Edward since his arrival, and the other engines warmed up to him. And on the Skarloey Railway, Rusty had proven himself to be a hardworking maintenance diesel. In the end, Percy decided that he just had to wait for himself on how Mavis would be.

A few days later, Mavis rolled into the quarry. She was black, had a cowcatcher in front, and her six wheels covered by side plates like Toby. She was greeted by Percy, Toby, and Sir TopHam Hatt.

"Welcome to The Island Of Sodor. I am Sir Topham Hatt, also known as The Fat Controller, head of this railway."

"Um, hello sir," called Mavis. "Pleasure to meet you."

"I'm Percy."

"And I'm Toby."

Mavis looked confused.

"Is there something wrong?" asked Toby.

"Oh, no, it's just, from where I'm from I don't see many steam engines, I'm mainly surrounded by diesels."

"Oh, I see," replied Toby.

Mavis looked puzzled by Toby's appearance. "To be honest, you look like a big brown box on wheels."

Toby felt insulted. "I'll have you know I'm a steam tram, and proud of it."

"I didn't mean any offence; I was only observing what I saw."

Toby backed down, but he was secretly still a bit upset.

"Right then," started Sir Topham Hatt, "your first job is to shunt those trucks for Toby to take out on his next train."

"Okay then," called Mavis "I've done this plenty of times before. This should be easy."

"Then there's not much to worry," called Sir Topham Hatt as he left on Toby, and Percy followed.

"Well, let's get started," she said to herself. She started trying to shunt the trucks, but the siding arrangements were awkward compared to what she was used to. Her driver agreed with her. So, Mavis made a decision. "I'm going to shunt the trucks the way I'm used to doing so."

When Toby got back, he was confused and quite appalled to see the way the trucks were placed. "What were you thinking?" he asked.

"The siding arrangements felt awkward, so I rearranged the trucks instead. I like rearranging things."

This made Toby cross. 'Trucks," he grumbled "should be where you want them when you want them."

"I was only making the job easier and trying to have fun," Mavis told Toby.

"Well, that's not the proper way we do things here," scoffed Toby.

"Aw, fiddlesticks," she grumbled and flounced away.

For the next few days, the same situation kept happening. Mavis tried again and again to get the siding arrangement right, but after a bit, she gave up and rearranged the train. After one week of this, Toby finally lost patience. "I can't spend my time playing hunt the trucks with you; take them yourself!" Mavis was pleased, taking trucks made her feel important.

At the station, Mavis met Daisy. Daisy noticed Mavis looked quite mad. "What's wrong?" she asked.

"It's that Toby!" Mavis complained. "He's such an old fusspot."

Daisy, showing signs of her old persona, spoke to Mavis on the situation. "Steam engines," she said, "have their uses, but they don't understand…"

"Toby says only steam engines can manage trucks properly!" Mavis interrupted.

"How absurd!" put in Daisy. "Depend upon it, Mavis, anything steam engines can do, we diesels can do better." Daisy knew nothing about trucks, but Mavis didn't realize this.

Toby's line crosses the main road behind the station, and for a short way, follows a farm lane. Frosty weather makes the muddy lane rock hard and very slippery. Toby stops before reaching the lane. His fireman halts the traffic at the crossing, and then he sets off again. By using the heavy trucks to push him along, he has no trouble with the frosty rails in the lane and across the road. It is the only safe thing to do in this kind of weather.

Toby told Mavis what she needed to do. "Now, when you get the farm lane, stop before reaching the lane, then the traffic will halt, and then you can set off again."

"I can manage thank you," she retorted. "I'm not an old fusspot like you."

Toby was offended beyond belief. "FUSSPOT! Wow, you really are a rude girl! I thought Sir Topham Hatt said you were nice!" And Toby fumed away.

The trucks were tired of getting pushed around by Mavis. "It's slippery," they whispered "let's push her around instead. On! On! On!" they yelled. Mavis took no notice. Instead she brought the trucks carefully down the lane and stopped at the level crossing.

Her driver waved a red flag. Just then Bertie The Bus came around on the right, and Terence The Tractor from the left, but they stopped when they saw Mavis. "That's one in the headlamp for fusspot Toby!" chortled Mavis. She was looking forward to her laugh with Daisy.

But Daisy never got her laugh. While she didn't realize it, Mavis had stopped in the wrong place. Instead of listening to Toby's advice, she had given the trucks the chance they wanted.

"Hold back! Hold back!" they cried.

"Grrrrr up!" ordered Mavis. The trucks just laughed, and her wheels spun helplessly. Workmen sanded the rails and tried to clear away the frozen mud, but it was no good. Everyone was impatient. "Grrrrr!" wailed Mavis.

Toby was in the yard when I heard the news. "I warned her, but all she did was call me an old fusspot!" he fumed.

"She's young yet," soothed his driver, "and…"

"She can manage her trucks herself!" interrupted Toby.

"They're your trucks, really," his driver replied. Mavis is supposed to stay at the quarry. If Sir Topham Hatt finds out…"

"Hmm…yes," thought Toby. He and his driver agreed that it would be best to help Mavis after all.

Meanwhile, a farmer came up to Mavis. He was red in the face and very cross. "I'll tell you just what you can do with your train! Take all that rock and dump it on yourself! That will be a sight to see". Mavis was indignant and very shocked by his harsh words.

Just then, she heard puffing noises. "Having trouble, Mavis?" chortled Toby. "I am surprised."

"Grrrrr!" said Mavis.

With much puffing and wheel slip, Toby pushed Mavis and the trucks back. The hard work made his fire burn fiercely, and his fireman spread hot cinders to melt the frozen mud. At last they finished. "Goodbye" called Toby. "You'll manage now I expect." Mavis didn't answer. She took the trucks the sheds and scuttled home to the quarry as quickly as she could.

That night, Mavis kept thinking about what had just happened. She felt very foolish and very cross at Toby. As the night went on though, she started feeling sorry about how she acted. She wondered if she had treated Toby properly. It was a hard night for Mavis to get through.

The next morning, she was still thinking about yesterday's events. She was resting in a siding, when Percy came to the quarry to collect some stone for his trucks. He saw how sad she was, and he didn't like seeing her look sad.

"Cheer up Mavis."

"I can't Percy."

"Why not?"

Mavis suddenly had an outburst. "Manager says I don't listen to advice! Manager says I have no business going down Toby's line! Toby's a fusspot!"

Percy was suddenly serious. "Toby has forgotten more about trucks than you will ever know. You must put the trucks where he wants them. Then you'll be a really useful engine. Now if you'll excuse me, I have to take these stone trucks to the harbor."

As Percy pulled away with his stone trucks, however, he thought to himself, "Did I sound too harsh? I never usually have outbursts like that. Besides, she's still new here, and it can take a while to adapt to change."

Meanwhile, Mavis was having similar thoughts. "I shouldn't have outraged like that on Percy. I sounded so rude to him. I didn't mean to. I'm just super stressed out and nervous after yesterday's events. Still though, why shouldn't I go on Toby's line?"

Mavis decided to listen to Percy's advice, but that was easier said than done. The siding arrangements were awkward. In order to put the trucks where Toby wanted them, she had to make several journeys. This made the work feel confusing, uncomfortable, and annoying. So, she started making a plan.

After the day's work had ended, she told her driver about it. "You know, if we use to the teeniest bit of Toby's line, we would save all this bother."

"You know what, Mavis. I think that's an excellent idea, and it would save the confusion." He left Mavis and next morning came back with some news. "I spoke to the manager last night, and he agreed we could go as far as the first level crossing." Mavis was delighted.

A few days later, the weather changed. As the snow melted, the quarry grew busy again. Some trains were so long that, before leaving the trucks for Toby, Mavis had to go beyond the level crossing with them. Now for her plan: she would go further down the line without it seeming her fault.

"Can you keep a secret?" she asked the trucks.

"Yes! Yes! Yes!" they all said in agreement.

"Will you bump me at the level crossing and told no one I asked you?"

"We will!" the trucks promised, but while Mavis was away, Toby arrived. He decided to shunt the trucks himself. The trucks decided to bump him anyway.

They reached the level crossing and Toby's brakes came on. This was the signal for the trucks. "On! On! On!" they yelled. Toby was away, with the trucks screaming and rattling behind him. No one realized that melted snow had turned the stream ahead into a torrent, and the bridge was in danger. Suddenly, a big log came rushing through, causing the bridge to weaken. The rails were now like a tightrope over the thundering water.

"Stop! Stop!" cried Toby. His driver fought control. They came nearer and nearer to the bridge. It was all or nothing now. The driver braked hard. Toby stopped, still on the rails, but with his wheels treading the tightrope over the abyss.

Meanwhile, Mavis came back and realized that her line of trucks was gone. Then, a dreadful feeling struck within her. "Oh no, Toby's taken them himself! I hope he's alright!" Against manager's orders, she went to look for Toby, until she found him and his trucks dangling over the bridge. Mavis was horrified. "Oh my gosh! Toby, are you alright?"

"For now, I'm keeping calm, but I'm in danger of falling."

Workmen anchored Toby with ropes while Mavis pulled the unhurt trucks away. Then she came back for Toby. "Hold on Toby!" she called. It was hard work, but at last, she was able to pull Toby to safety.

"I'm so, so sorry about the trucks. I can't begin to fathom how you managed to stop them in time."

"Oh well," said Toby "my driver told me about circus people who walk tightropes, but I didn't fancy doing it myself."

"No, really Toby,", sighed Mavis, "I'm so sorry for being such as stuck-up and feisty engine. You're not an old fusspot at all."

"And I'm sorry I was so cross," Toby said. "You are a young newcomer and I just got annoyed."

"Ah well, we live and learn," Mavis said.

"And Mavis, if you ever need some assistance, I'll always be there to help you out," Toby said kindly.

"Thank you, Toby." The two talked for a bit. Then, Mavis remembered Percy. "I'm off to find Percy now! See you, Toby!"

Mavis went back to the quarry, where there, she met Percy. "Percy…" but before she could continue, Percy spoke up.

"Mavis, I'm sorry if I sounded harsh on you back there. I know you were under a lot of stress and are a newcomer here."

Mavis then spoke up. "Percy, you're right, I was stressed out, and I'm sorry I outraged at you. It's not something I do a whole lot."

"Neither do I, actually, in fact I'm quite the opposite. I only get that mad if I see one of my friends being insulted."

Percy and Mavis had a moment of silence, then Percy looked up at her.

"Friends?" he asked.

"Friends!" Mavis said in delight.

Just then Sir Topham Hatt arrived. "A very smart piece of work. Mavis, you did well too, I hear."

"It was my fault about the trucks, though, sir."

"Yes, but quickly rescuing Toby made up for it."

"Sir, I was wondering if I…"

"Could what"

"If I…could come down the line sometimes. Toby says he'll show me what to do."

"Certainly," smiled The Fat Controller. "I understand being stuck in a quarry all day isn't the most exciting of all jobs. I'll speak with the quarry manager on the matter."

A few days later, it was decided that Mavis would help Percy and Toby deliver the goods on Thomas' branch line. Mavis was pleased to hear this news, and she thought that life would never get better. Little did she know; this would only be the beginning.