Thomas the Tank Engine was leaving for another trip around the world and many of his friends had come to see him off. "Good luck, Thomas," said the Fat Controller. "I hope you enjoy yourself and show everyone what a Useful Engine you are."

"Yes, Sir," Thomas replied.

"Goodbye, Thomas!" Percy whistled bravely.

"Goodbye, Percy!"

The engines cheered and whistled as Thomas was loaded and the ship drifted away from the quayside. Percy had to collect some goods from the next ship coming in and he watched Thomas' ship sail away until it was out of sight.

Nia had been sent to do Thomas' work while he was away, and Annie and Clarabel enjoyed themselves. Percy's work carried on as usual, but he couldn't stop thinking about Thomas. I hope he's safe out there at sea, he thought.

That evening, Percy backed into his berth at Tidmouth Sheds. He looked at the empty berth beside him and thought of Thomas again. Suddenly, he heard a bell.

"Good evening, everyone."

Percy was surprised. "Toby, what are you doing here?"

"I knew you would be missing Thomas, so I thought you could use some more company."

"But what about your work at the Quarry?"

"Don't worry, Percy," Toby replied. "You know I collect the quarry workers from Knapford anyway."

"And your stone trucks?"

"I only bring them down if there are any. It saves time and gives Mavis more room to work. They can always be collected later. I thought it would be best to join you here while Thomas is away. Besides, Henrietta can catch up with Annie and Clarabel and we'll get some extra rest in the morning."

Percy smiled. "Thank you, Toby."

Toby smiled too. "It's always nice spending the night here," he said. "It sure brings back memories."

"What do you mean?" asked Nia.

"You know those Sheds by Tidmouth Station?" Toby explained. "Thomas, Percy and I used to sleep there a long time ago. It was where I usually slept until my Branch Line was reopened.

"So, you and Thomas have almost always stayed in the same Shed?" asked Rebecca. "No wonder your such good friends."

"Well, they weren't always," said Gordon. "After Thomas was put in charge of his Branch Line, he became very full of himself and thought he knew best."

"I remember that," chuckled Toby. "Thomas and Percy didn't always get along back then either.

"How long did that go on?" said Nia curiously.

"Quite a while," replied Toby, "but it was actually a small problem where it all seemed to end."

Rebecca was interested. "What happened?"

"We'll tell you." And with that, Percy and Toby began.

One evening, Percy was bringing empty stone trucks from Tidmouth Harbour. He had had a good day and was feeling very pleased with himself, but he was so busy thinking how he would tell Thomas and Toby about his day's work that he forgot to watch where he was going. Suddenly, he saw a broken tree branch hanging over the line right in front of him.

Percy tried to stop, but it was too late. The branch hit his smokebox, broke away from the tree and fell to the ground. "Ouch!" Percy cried. He was more startled than hurt, but his front was still sore when he got back to the Branch Line Sheds.

"It's your own fault," said Thomas huffily. "You should keep a better look-out. I've no patience with you."

"Pah," retorted Percy huffily and talked to Toby for the rest of the evening.

Percy didn't speak to Thomas the next day either. The evening started the same way.

"I say, Toby," said Percy, "what's a drip? Do you know?"

Toby pondered. "It's when water comes through a small opening somewhere in small drops," he explained, "like when rain comes through a hole in your cab and your Driver and Fireman don't have time to mend it.

"That's silly. I heard a boy on the platform call his friend one this afternoon. I'm sure he couldn't have come through a hole in my cab."

Thomas was tired of being ignored. "That's different," he interrupted loftily. "The boy just thought his friend was being silly, a coward or a spoilsport."

Percy thought. "So, if you stopped me from doing something nice, would you be a drip, Thomas?"

"You're the drip," said Thomas crossly. "Now, go to sleep like a sensible engine and stop talking nonsense." Percy was offended. Instead of going to sleep, he was determined to pay Thomas out.

The next day at Elsbridge Junction, Henry's train was late. Thomas set off along the valley trying to make up for lost time. He was nearing the river outside the Station when suddenly, there was a loud 'bang', and something hard hit the bottom of his left water tank. "Ouch!" exclaimed Thomas and stopped. As he did, he felt cold water splashing against his wheels.

"One of your coupling rods has broken," said his Driver. "It swung up and punctured your tank. We'll have to get help."

Percy was busy shunting when the Stationmaster came up. "Leave those trucks, please, Percy. Thomas has a hole in his water tank. There's water dripping everywhere, and he can't get home on his own."

Percy was still cross with Thomas. "I won't go," he huffed. "Thomas thinks I'm silly and called me a 'drip.' He can stay there and drip himself."

"But what about Annie, Clarabel and the passengers?" said his Driver. "Do they deserve to stay out all night too?"

Percy was sorry at once. "I forgot them. We must rescue them in case they turn into drips too." And he hurried away.

Everyone was glad to see Percy and the passengers thanked him. "I'm sorry I was rude," said Thomas sadly. "That tank of mine turned me into a bigger drip than we expected, didn't it? Can we be friends again, please?" Percy was delighted to agree.

"After that, Thomas learned sense," smiled Toby.

"And we became better friends," added Percy.

"And I'm sure your Branch Line was all the better for it," replied Nia.

"Indeed, it was," smiled Percy sleepily. "Indeed, it was."