Things have been full of changes and surprises in the kingdom of Arendelle. Three years ago, Elsa, the daughter of King Agnarr of Arendelle and Queen Iduna of the Northuldra people from the Enchanted Forest, had been coronated to the position of queen upon turning twenty-one. Her younger sister, Anna, served as princess underneath her, and her boyfriend, Kristoff, was respected upon the citizens like a prince.

Only recently, Elsa and her friends had traveled to the Enchanted Forest to find Elsa's true destiny, and she stayed there to become a protector. Her abdication of the throne swore Anna in as new queen, and her engagement to Kristoff and subsequent marriage made him her king. Even so, Elsa still remained close to her sister and newfound brother-in-law, as well as to the people of her kingdom.

One particular day near the end of autumn, Elsa was in the Enchanted Forest alongside her fellow guardian, the Nokk. Including Elsa herself, the Enchanted Forest was protected by guardians, each resembling one of the four elements: water, earth, fire, air, and Elsa being the spirit of the fifth element: ice. The Nokk was the water spirit which took the appearance of a horse, and it had been tamed by Elsa to serve as her trusty steed.

Elsa was gently stroking the Nokk's body, which was solid despite its watery appearance. "Today's the day," Elsa said to herself. "It's Friday, so it's charades night."

The Nokk whinnied in response, and after the two had made peace, they began to understand one another.

"You're right, Nokk," Elsa told it, "I should make myself look pretty for tonight. I wouldn't want Anna to think I just got out of bed."

Using her powers, Elsa summoned a mirror of ice in front of her. Then, she fixed her hair and tied it into her signature braid, which she had originally lost on her previous journey. She still liked it, so she would save it for special occasions.

Just then, the other three spirits, Bruni, Gale, and an Earth Giant, came up to Elsa. The fire spirit, Bruni, was an adorable little salamander who had power over fire. The Earth Giant was one of a group, who together served as a whole of the earth spirit. And Gale, which was really a bunch of leaves and debris that often gathered up in a harmless tornado, was the wind spirit. They, along with the Nokk, had all initially been hostile towards Elsa and her friends, but they eventually accepted her as one of them, and came to acknowledge her friends as their friends.

Even though none of the spirits were shown to talk, Elsa understood them completely. "What's up, you guys?" she asked.

Gale used its power of wind to summon a bunch of leaves into the form of a calendar, and then used a bunch of sticks to create crosses across seven of the boxes. Then it used the leaves and sticks to create a picture of the palace of Arendelle. Apparently, it was telling Elsa to take some time off and stay with her family.

Elsa smiled. "Oh, you guys," she said, "I would absolutely stay a while with Anna, but can you all look after things without me for a while?"

Bruni spat a stream of fire into the air above it, and the flame changed its shape into the form of a four-pointed star. Each of the points bore the symbolic shape of one of the four elements within it, and the symbol of ice formed in the very center. Then, Bruni shot another ball of fire into the air, forming a round shape beside the star.

Then, Elsa heard a siren's call within her head, just like what had summoned her to the Enchanted Forest before. "Oh, I see," she said, "if I'm needed here, then the siren's noise will wake me from my slumber, and I will see this shape within the sky. That's how I'll know when I'm needed here."

The Nokk and Bruni nodded.

Elsa was pleased to have her fellow spirits looking out for her and the rest of the Enchanted Forest. "Okay, then," Elsa said, "I guess I'll go get changed and gather my stuff, and then I'll head off."

The Earth Giant used its powers to summon a large boulder in front of Elsa. The boulder had an opening with a duffel bag and a chest inside, and Elsa had a lot of her clothes stored inside it. They included, but were not limited to, her coronation clothing, her ice dress from when she ran away from Arendelle, her purple autumn dress from last autumn, her springtime dress from Anna's nineteenth birthday, her winter coat from the Christmas she spent with Anna since her coronation, and even her initial clothes from her journey to the Enchanted Forest.

Elsa looked pleased as she went into the rock and began packing her clothes into the duffel bag. "You guys think of everything," she smiled.

Once Elsa had packed her clothes and gathered her suitcase, she climbed onto the Nokk's back, and the Nokk grabbed the duffel bag and placed its shoulder strap around its neck. Then, it stood on two legs and whinnied, and then it galloped towards Arendelle. Because it was the water spirit, the Nokk could walk upon water.

The other spirits watched as Elsa rode off into the afternoon, returning to her original home. They were pleased for her to stay awhile with those she loved, and they had a way to call her back if she was needed.

In no time at all, the Nokk arrived at the bay beside the palace. The horse spirit galloped around to the kingdom's town entrance, and then it trotted through town towards the palace gates. As Elsa looked around, she could see all of her kingdom's people happily going about their day, and all pleased to see her.

Once the Nokk arrived at the door to the palace, it came to a stop, and Elsa climbed off of it. Then she took her duffel bag off its neck, and the horse bowed to her.

"Thank you, Nokk," Elsa said gratefully, "and good luck. If you need me, just call."

The Nokk whinnied in response, and then it jumped from the bridge to the water, and it set off for home.

Elsa picked up her duffel bag and walked up to the door, and then she knocked on it. "Your Highness," she called, "I'm here."

"Coming!" a cheerful voice called out. A few seconds later, the doors opened, and there was Anna. She had a lovely green dress on, and a beautiful flower in her hair. "Elsa!" she smiled. "You're here!"

"Wouldn't miss it," Elsa smiled, and she and her sister laughed as they hugged.

Then, Elsa saw Anna's wedding ring on her left hand. The gemstones embedded into it glistened like stars in the night. "Anna, that's a beautiful ring," she said to her sister. "Did Kristoff buy that for you?"

"Yes," answered Anna. "But what a surprise, I didn't expect you here until later this evening."

"Well, the spirits insisted I took some time off and come by for a visit," Elsa said to her. "That's okay, right?"

"Of course, Elsa," Anna smiled, "you don't even have to ask to come stay. Whatever happens, as long as I'm queen, this palace is yours, too." Then, she stepped to the side. "Come in, come in," she said happily.

Elsa walked in, and the doors closed behind herself and Anna.

Inside the palace, Kristoff, Sven, and Olaf were waiting. Once Elsa saw them, she walked over to hug each of them.

"Kristoff, Olaf, Sven," Elsa said as she hugged her family, "I've missed you so much."

"We've missed you, too, Elsa," Kristoff said happily.

Olaf looked especially happy. "There's a funny thing about why I like warm hugs," he said, "it's that hugging actually provides an enhanced sense of belonging and trust as well as love or affection. It's also part of the reason why many people feel happy after a hug, and longer ones provide stronger feelings."

Anna giggled at Olaf's comment. "That'll be great to remember, Olaf," she said happily.

"By the way, the spirits told me to come stay for a week before I head back," added Elsa. "I guess we've come to understand each other so quickly. They also have a way to quickly call me back if I am needed."

"Well, as long as you're sure they'll be okay, I don't think we'll have to worry about anything, then," Kristoff replied.

"You're right, sweetie," agreed Anna, "we'll be okay as long as the guardian spirits are safe." Then, Anna looked at her sister. "Well, since you're here early, Elsa, why don't we do something extra special for dinner?"

"I think that'd be great, Anna," Elsa agreed.

"And then, for dessert, we can have something made with the extra sweetness of…" Anna began, and then she and her sister breathed in through their noses.

"Chocolate," the two sisters said together, contentedly. Then, they set off together with Kristoff, Olaf, and Sven to their palace's kitchen.

Meanwhile, over on the Island of Sodor, it was late in the afternoon, and work was already winding down for the evening. Thomas the Tank Engine was at Knapford Station with Sir Topham Hatt, the railway controller. Thomas had been working hard on railways all across the world lately, so he was happy to come home for a change.

Three years ago, Thomas had been summoned to Arendelle by Elsa to help her stop a perpetual winter during the summer, which was summoned by a mysterious woman named Glacia. As they went on in their battle, Elsa and Thomas learned that Glacia had perished long ago in a snowboarding accident, back when she was once dating Sir Topham Hatt. The snow and ice kept her alive, but her life energy became completely dependent upon it, and it turned her to evil. Glacia had nearly killed Thomas by freezing his heart, but thanks to his strong willpower, Thomas had stopped her and unfrozen her life energy, causing her to fade away. Ever since then, Sodor and Arendelle had remained close allies.

Things had changed a lot on the Island of Sodor over the past three years. Edward the Blue Engine had moved out of Tidmouth Sheds to live in Wellsworth Sheds with Philip the Diesel Boxcab near his branch line. Henry had also eventually moved out to live in Vicarstown Sheds on the other side of the island. In exchange, two new female engines, a Kenyan tank engine whom Thomas met on a world journey named Nia, and a newer, yellow tender engine from the Mainland named Rebecca, had moved into Tidmouth Sheds.

Also, down at Brendam Docks, a brand-new crane named Carly had arrived to help Cranky and the other large crane, Big Mickey. At first, Cranky and Carly had some difficulty getting along, but they eventually became firm friends. Finally, the Sodor Construction Company, led by Miss Jenny Packard, had purchased two new female vehicles: a turquoise female bulldozer named Brenda, and a yellow, drilling engine named Darcy.

Sir Topham Hatt was holding a clipboard in his hands as he spoke to Thomas. "Okay, Thomas," he said, "you have done a good amount of work today. Now, I just have one more job for you."

"Yes, sir," Thomas said eagerly.

"Percy has broken down, so I need you to deliver the mail for him tonight," explained Sir Topham Hatt. "The mail route will be especially longer than usual tonight, so it will most likely take you into the night to complete it. But the weather report says that heavy rain is coming tonight, so you must be extra careful with the mail vans."

"Of course, sir," Thomas declared, happy to help his best friend.

As Sir Topham Hatt left, Thomas heard a whistle. Just beside him, he saw Percy being pushed by Rebecca. Her signal was red, so Rebecca braked as hard as she could, but she slipped too far beyond the signal. Embarrassed, she reversed back into the station.

"Hello, Percy, hello, Rebecca," Thomas said to his friends.

"Hello, Thomas," said Percy, a little sadly. "I don't like breaking down when I have mail to deliver."

"Don't worry, Percy," Thomas said to his friend, "I'm going to deliver your mail tonight." Then, he looked at Rebecca. "Oh, Rebecca, that reminds me, I probably won't be back until very late tonight."

"Nothing to worry about, Thomas," Rebecca told him. "The only thing is, I also have to go to the Steamworks myself. James told me the story about his brakes and why Edward moved out of Tidmouth Sheds, so he suggested I have mine checked so I don't make the same mistake he did. But Nia should be coming in any moment now, so you should tell her about your job."

"Okay, I'll do that," Thomas agreed.

Then, Rebecca's signal changed to green. She tooted her whistle, and she set off, slowly and carefully, pushing Percy to the Steamworks. As she left, they heard Thomas calling out to them:

"Be careful! Sir Topham Hatt says it's supposed to rain tonight!"

A few minutes later, Nia came into the station on the same track. She pulled up beside Thomas and came to a safe stop. "Hi, Thomas," she said to him.

"Hello, Nia," Thomas told her. "This works out, because I wanted to tell you, I'll be very late coming home tonight. I'm doing Percy's main run for him, and it'll be extra long."

"Okay," said Nia, "I'll tell the other engines when I get back. But before that, I wanted to ask you something."

"Okay, what is it?" asked Thomas.

Nia had a framed picture on the front of her smokebox. "Who are these people with you and Rosie in this picture?"

Thomas looked at the photo, and he saw what the picture was. It was a picture of him, Rosie, Elsa, and Anna from three years ago, before Elsa and Anna returned to Arendelle after defeating Glacia. But Nia didn't know them because Thomas's journey to Arendelle took place before he met Nia in Africa for the first time, and he hadn't told any of the island's newcomers that story, either.

"Well, that's Elsa and Anna," Thomas answered. "They're my friends."

"Your friends?" asked Nia. "Well, I've never seen them around here. Where on the island do they live?"

"They're not from Sodor, Nia," answered Thomas, "they're from a kingdom, far away, known as Arendelle. It's near Norway."

"Norway?" asked Nia. "I don't remember traveling that way when we were out on our world trip. Maybe you could take me sometime, Thomas?"

Thomas thought for a moment. "I'll see what I can do, Nia," he promised. "Anyway, I'd better get going. I have to deliver Percy's mail tonight, and it's supposed to take a very long time. I would like to get the job done as quickly as possible so, hopefully, I can get back before it rains." He tooted his whistle, and he set off to collect the mail.

"Good luck, Thomas!" Nia called to him as he started away. Then, she set off for her last train of the day.

As Thomas puffed along the line, he began to think about Elsa and Anna again. He hadn't seen them since a while before Elsa left Arendelle to protect the Enchanted Forest, so he didn't yet know that Anna had become queen, or that she and Kristoff had gotten married.

But as the sun started to set behind him, the wind began to blow gently. At first, everything was normal and quiet, but then Thomas heard a sound. It sounded like someone was singing, but the sound was very brief.

Thomas looked around, but he didn't see anyone. "Hello?" he asked. "Is someone there?" But the noise didn't answer back, so he kept going. "Oh, well," he sighed, "I guess I must be hearing things."

But Thomas was wrong. The noise he'd just heard wasn't random: It was the sound Elsa had heard which summoned her to the Enchanted Forest… and now it was calling him.