From the tower there was something almost otherworldly about it. She vaguely recalled something she had read about in one of her father's old books; about a form of theatre where a giant white sheet of paper, dozens of feet wide and tall, was erected into the stage. A fire was lit to cast a light, and the entire performance took place hidden behind the sheet, projected only as pitch-black shadows. She had been fascinated in the way only curious children could be, and she and Anna had spent an entire afternoon finding the biggest white sheet they could and some sticks for a small fire. Elsa had watched enraptured as Anna and the servants had performed a play right there for her. Far easier to believe in monsters and dragons without being able to see the raggedy collection of sticks and clothes they had been made out of. The performance had ended when an excited Anna had stepped too near to the fire and scattered it, making a huge fuss and consigning them to their rooms for a week as punishment for scorching the floors.

The fires that raged through the town below her had the exact opposite effect of that shadow performance. Distance turned the very real disaster happening far below her into something unreal, something she had trouble accepting as actually happening. If Elsa squinted she imagined she could see individual people as small tiny blobs as they ran to and fro on the streets, contrasting with the whites and blues of the snow that still covered the streets and houses. Those colours though were rapidly being replaced by red, as the fires spread from house to house, melting away the snow.

She still felt the ghost of Anna's touch on her arm from where her sister had held her. Anna was long gone, had already pushed her way through the throng of nervous and scared nobles, running for her horse and shouting for the guard to follow her. Elsa now stood alone – the preening and shaking princes behind her certainly didn't count as company – and watched as below her, her country was burned.

She heard the mutterings behind her – are we safe here? What is going on? Is this war? Who? What? How? – and turned to face her audience. She knew she should feel uncertain or just as afraid as them. Maybe even just a few hours ago she would have. It was as if the strength of the mountain she had felt when the crown was placed onto her head hadn't yet left her, and as she stared at the row of fearful faces she felt little but…contempt? She couldn't even tell which of them was which. They had all just become a collection of frightened faces and shivering bodies.

"Your majesties…" she said, but got no further.

"What is going on your gra- your majesty?"

She took a breath and felt the icy-cold air enter her lungs. For a half-second it hitched there and she feared she wouldn't be able to speak, but she thought about Anna, already racing down the mountain to go to her – to their – people, and her voice came out smooth and powerful. A queen's voice. "Just a problem I thought I had solved, your grace," she said. Not the voice of a princess telling a diplomatic lie she hoped nobody would question, but the voice of a queen with full confidence.

It worked. "Will we be safe here?" someone asked with a nervous quaver in his voice.

Elsa took a step down from the raised dais her throne sat on, and smiled. "You are all under my complete protection."

"Or under your power?"

Elsa's eyes slipped sideways as the voice spoke. The other nobles shuffled out of the way between her and one who had spoken, as if his voice had shoved them aside to let their eyes meet. "Your majesty?" Elsa addressed the King of the Southern Isles.

Nothing fearful in his voice at all. He stepped forward and the other nobles parted before him, until he stood before Elsa, looking slightly down at her. "It is true, is it not?" the King spoke. "As you have taken very great pains to make clear, up here we are entirely within your considerable power?"

What on earth is your game? "And no harm will come to you in it, your majesty. You are my honoured guests, and as Queen of Arendelle I promise, no harm will come to you."

"Your guests, or your prisoners?"

The horse shivered below her so much she almost fell from the seat as she pulled up beside the outskirts of the town, hooves slipping in the melting snow that Anna barely had time to dismount and step aside as the beast fell sideways, laying panting in the muddy grass underneath.

She spared a single thought for it – attaboy – as she spirited from it towards the row of homes and fences that marked the entrance to Arendelle's biggest town, not even thinking about a subtler and maybe safer approach. Anyone wanting to find her would just need to listen for the fast clanking of her armour as she ran.

The whites of the snow had been burned away now, replaced with the browns and greys of cobblestones and the reds of the fire which licked at her and warmed her steel armour as she ran through the town. A town like Arendelle which saw colds far more than it ever did warmth was ill-prepared for the fires that roared through it, jumping between the roofs of homes built close together.

"YOUR GRACE!"

Anna spun as she heard the voice, one hand already on her sword. A man in brown leathers ran towards her and for a second she almost drew her blade, but then sunlight reflected from the thin iron chain around his neck, and she stood straight as the man drew up before her and knelt. "Up."

Anna couldn't see herself but from the man's point of view he raised his glance to see some incarnation of a goddess before him. Her helmet lost in the mad dash down the mountain, red hair billowed in winds created by a dozen fires, framing a pale face and two emerald eyes set into it.

"What's happening!?" Anna said, having to shout. She had never seen so much fire before, and was shocked at how loudly she had to yell to be heard over the sounds it made; the crackling of kindly, roar of collapsing stonework as wooden supports were burned away.

And the cries and screams of course.

The man pointed and Anna followed his finger. Beyond the rooftops she could see the tall masts and sails of the ships at harbour in the docks. Some it seemed had been further out on the quays and so had time to furl up before the sparks reached them, but closer to the docks themselves there had been no such luck, and the entire docks was almost a wall of flame as the huge flax and cotton sheets burned ferociously.

"The fires began at the docks- " the man cocked his other hand back to point, "-and from the older parts of the town your grace."

Empty warehouses, abandoned or half-built homes. Arendelle expanded slowly and buildings could have their walls finished for months before the insides were complete. Anna began to have a sinking feeling inside her stomach.

"And the rest?" she asked, already knowing the answer. Many bodies were burned, seared black by fire. But others had no touch of fire. They had been cut down.

"Set by the soldiers," the soldier said. "They came from the docks armed and started throwing pitch and torches as they went. Things were burning before we knew we were under attack."

And half the soldiers were on the mountain for the coronation! Anna could have screamed. "Where are they now?" she asked, her voice hoarse.

"Inside the castle walls, already across the moat. They're proclaiming…well…"

She felt a rising fire inside her breast, hotter than all the ones around her. Hot enough to burn her up. "What are they saying?"

The man swallowed, either from the need to breathe in the ever-rising heat of the air or from the look in his princess's eyes. "They're proclaiming an end to the tyranny of the demon queen, and re-establishment of order under a new regent."

"Who?"

"I speak plainly, your majesty, nothing more," the king said.

"You're speaking nonsense, your majesty," Elsa responded.

"Why this ice-palace, far away from your father's castle, if not for secrecy? Why your soldiers here, if not for guards?" The king swept an arm to encompass the room and everything inside. "Why any of this, except for maybe not a coronation, but something more…sinister?"

"Are you implying this is some kind of plot?" Elsa asked. She could feel ice licking at her fingertips, as if her power was a faithful dog at her side, just begging to be let off the leash. She tried to take a deep breath, but the cold air suddenly seemed far too cold. The strong pulse she had felt within her breast only minutes before now felt hesitant. As if with just a steely gaze and a few words the King of the Southern Isles had stripped her crown back from her and turned her only again into Princess Elsa.

Instead of answering her, the king instead spun around, his cloak flowing around him, to face the other nobles, placing himself between Elsa and them. "Your most noble majesties! Were we not all warned? Were we not all informed of the happenings in this strange and ungodly country?" He threw back a hand at her. "Did the spies and priests not tell us?"

"SILENCE!" Elsa yelled, but it was as if she spoke to a wall.

"Maybe we were fools to come here!" The King turned back and spoke clearly and deeply. "To trust the words of a demon," he said, and Elsa heard in her mind the word written on walls by whispering rumours and maddened priests. The word they had used to justify the burning of villages and the murder of innocents.

She felt as if she had had her breath taken away from her, and as it all became clear in her mind Elsa was the one who felt like a fool, as she looked from man to man, and saw their attention directed not at her but at the King who stood before them, yelling and carousing. "It was you."

It took every inch of discipline she had, but she mustered it, turning away from the king and back towards the balcony from which she had first seen the flames lick at her town. They were higher now, the fires reaching across most of the city. The docks were invisible now, just one giant conflagration of burning boats and homes. The black fuzzy shapes of people were nearly invisible now, except at certain points. She could see at the bridge that joined the town to the castle a collection of swarming dots as something happened there, and somehow she knew that Anna was one of them. She wasn't looking at that though, and tore her gaze away. It took her a few seconds to adjust from the harsh reds of the town, but eventually she saw them. On the white and blue sides of the mountain, moving slowly but purposefully, what could have been fifty or sixty men crawling their way up the path she had formed for the procession, coming up to the palace.

"Your troops," she said, not really a question.

"Our rescuers," the King said. Looking directly at Elsa on the balcony and therefore facing away from the other scared and worried nobles, she was the only one who saw his normally placid face turn into a smile.

She moved through the town like a bright spark slowly being turned away and turned to ash. Every breath came just a little bit harder and harsher in her lungs than the previous one. She felt like the air above her had turned into a solid weight, and had to constantly resist the urge to bend her knees. The fire had spread from roof to roof, faster than Anna would have thought possible. Houses made up of wood and stone went up in blazes as decades of dirt were freed from within walls and rooves, swirling through the air and turning the middle of the day into a world of dark greys and hazy streets.

The men who struggled through the billowing smoke behind were worse off than Anna was, if anything. They had only loyalty and duty to uphold them, whereas Anna had not only those but also a chill inside her that simply would not allow her to stop. She felt her chest tugged slightly behind her, as if Elsa was standing just behind her rather than away at the ice palace. It gave her strength.

Ahead of her some dark shapes detached themselves from the wall of back-lit grey that was Anna's vision. She already had a hand on her ice-blade's pommel, but released it when the shapes came closer and turned from blank nothings into soot-coated Arendelle soldiers. They saluted as she approached.

"What's happening?"

Anna listened as the man in front choked and wheezed his way through an explanation: "Word came from the docks within a few minutes y'majesty, but people thought it was just an accident or somethin' at first." The man gestured from the wall of flame – visible even at this distance and through all the soot, ash and dust in the air – over to the centre of the town. "Then someone noticed the people runnin' out were all wearing the same uniform, and tossin' lit torches and buckets of something onto the houses next to 'em."

"They were in the boats and used the panic to spread it before you realised it was an attack?"

The man fingered the iron runestone at his breastbone. "Aye y'majesty."

A trick! A low-down rotten dirty trick! She looked down at the nervous man. Maybe he had been one of the first to notice them? Had he not paid attention, thinking they were simply more revellers? "It's not your fault man," she said, "only our invaders."

He looked relieved, the runestone he had been nervously rubbing dropping back to hang as he let go. "What're our orders ma'am? We can't find any officers in all this soot, we're blind and deaf in this mess!" He was shouting just to be heard now.

Anna could only vaguely see the fire through the dense matt-grey world, but she could feel it spreading around them. She resisted the urge to say something impulsive, something stupid. She had always been the faster one, the one who wanted to get stuck in and get things done. But Elsa was miles away and she needed to be a leader now.

If I was an invading army…

Where would she go? Assume they had expected complete victory (don't think about the fact that this handful of men may be all that's left of our armed men), what next? She took a deep breath, even in spite of all the particles in the air, and tried to think like not like Anna the princess, but like Anna the leader. It didn't take her long for an answer to come, so clearly it couldn't be anything but right.

After invasion, occupation.

She looked at the men around her. "They'll have gone to the castle."

"The castle, ma'am?" one of them said, and Anna heard the fear in his voice and the thoughts in his head. Arendelle's castle was built across a huge bridge, separate from the rest of the town. The ash would probably coat it but the fire would never reach it. Even though it hadn't seen war in centuries and the walls were hung with paintings and the cabinets filled with cutlery and books, it was still a monumental stone edifice, designed by her ancestors to very much repel an army.

She looked him dead in the eye. "Our castle." her gaze swept to encompass the dozen or so men standing around her. Most of them were older than she was, all of them had been soldiers longer than she had, but every single one of them stared at her, enraptured. She made a decision. "Our people's castle." She felt the beginning of a plan forming in her mind, and gave a smile so full of confidence that right then and there the soldiers had all their worries utterly thrown from their minds. "And our people are going to help us take it back."