Two years ago, Rhine Lab's Christine Wright split the sky over Trimounts. From that night on, all of Columbia went utterly sky-mad.

From baby strollers to nomadic cities, everything got a propeller bolted on, and any stock or liquor with 'sky' in the name shot up in price. The crystallization of that craze is a science park floating 600 meters up: 'Propeller Paradise.'

And into that dazzling paradise step two people from opposite ends of the world. One is Fen, a tour guide who only takes on the 'impossible.' The other is an elderly banshee who's crossed the Wasteland of Death.

1. The company that opened the sky is, of all things, stuck underground

The park's original proposer is Rhine Lab. And yet Rhine Lab's own ecodome has been pushed to the ground level — right next to an unremarkable dirt pit, no less.

The one keeping that ecodome running is Nasti Runoray. A banshee from Kazdel and the section chief of engineering — few words, quick hands, and someone who eats brick-hard hardtack for lunch.

Her assistant Sky is the exact opposite. A young man who clawed his way up from the slums and idolizes Christine, he grumbles daily about why nobody remembers her.

Nasti answers flatly: recording and looking back is a historian's job. We just have to keep moving.

2. Mr. Smuggler-Director, and a fake docent (the real one's in prison)

The park's director, Gordon Tannen, is a very special businessman. Mocking the rule that only Columbian-made parts may be used, he smuggles in banned Originium devices from other nations, mounts them as 'hearts' on corporate exhibits, and pockets the profit.

Into that park sneaks the tour guide Fen. She got hold of the résumé of Oakley, the real docent who'd just gone through a breakup, and infiltrated under that identity. Her motive is pure — she's searching for a way to restore her client's, an old banshee's, fading memory.

But of all times, that very banshee client vanishes from her room without a trace.

To make matters worse, the real Oakley shows up at the director's office shouting, "I'm Oakley," and Gordon spits out the champagne he was drinking. The fake docent had already made contact with half the park by then.

3. A tree that must die to live (the ecodome was built to die from the start)

Soon, disaster strikes the ecodome. Seventy-two mature trees and three hundred fifty saplings wither and die in five minutes flat.

On the surface, it looks like Fen's fault for pulling out a 'twig' stuck in one of the trees. But that twig was actually Nasti's Bonequill — the key that runs the entire ecodome.

What's more, Gordon had guards posted at the door even before the disaster happened. This catastrophe wasn't an accident — it was a script written from the very start.

And quietly, one truth surfaces here. What Rhine Lab actually wanted wasn't for the plants to 'live' — it was for them to 'die,' the way a banshee understands dying. All so that one very special tree could live.

4. The secretary's true identity, and a tree that rises into the night sky

Gordon's secretary Mercia is someone who recites 'secretarial protocol' no matter what happens. But there's a different reason behind her composure — she's a special agent of Maylander, the foundation that 'manages' Columbia's accidents.

Meanwhile, as Muelsyse uses a water clone to scare off intruders by impersonating 'Nasti' — a saluting, cheerful Nasti even makes Gordon flinch — the real incident breaks out.

The sealed basement collapses, and a colossal 'tree,' woven from rotted wood and metal, rises silently into the night sky wrapped in a faint glow. No propellers, no engine sound.

The secret Rhine Lab has staked its life on hiding is revealed to all of Columbia, at the absolute worst possible moment.

5. A lie two hundred years old (why the Canyon has been quietly rotting)

The old banshee's name is Vayla. And Fen's client, it turns out, had actually come all this way looking for Nasti.

Two hundred years ago, Kazdel was swept up in the Allied Forces' steel and gunfire. Fewer than a thousand banshees survived, and half of those lost their voices.

A war in which the very people who conduct funerals couldn't even finish singing an elegy for their own dead.

The survivors, Vayla and Lakeramalin, built the Canyon beyond the Fog Lake. A life with no war, no death — only songs and desserts. Proof that banshees could set aside their nature and live differently.

In exchange, Vayla secretly intercepted the 'tokens' of death arriving from outside the Canyon for two hundred years — at the cost of leaving the ungiuded souls with nowhere to return.

And the banshees who defied their nature slowly turned into hollow shells during a long, agonizing bout of forgetting, right before they died.

6. The day Nasti didn't look back

The child Vayla brought to the Canyon was young Nasti herself — a girl raised in Kazdel, and so the very first one who would see through the lie.

If it's just an accompaniment for a smile, you don't need a bone flute.

— Vayla

An accompaniment for laughter needs no grand instrument — that's what she meant. A single quiet phrase that lingers a long while.

But Nasti already knew that the Canyon stood on a fragile lie. So she decided to leave and find an answer — one that had to exist somewhere outside the Canyon, outside Kazdel.

On the boat of farewell, all Vayla could manage was, "Eat well, my daughter."

Nasti never once looked back, taking in only her mother's face reflected on the water.

And she said a small goodbye. "Farewell... Mother."

7. But this park was doomed to fall from the very start

Maylander's veteran agent Tin Man tells Mercia the truth. The hearings kept getting postponed, and it was no accident.

Columbia's sky craze is red-hot but completely useless. In an age where Kazimierz arms its knights with powered exoskeletons and Leithanien teaches children Arts warfare, Columbia has been left building nothing but floating carousels.

So Maylander's plan is this: bring down 'Propeller Paradise' disguised as 'a foreign spy's terrorist attack.' Then the passion for the sky will turn, for the first time in eighty years, back into rage and armament.

The contraband Gordon smuggled in was, in truth, foreign military components hand-picked by his mentor Gustave. Even Gordon had been someone else's chess piece.

But there was one crack in this perfect script. Mercia.

She grew up in the estate of Selene, the foundation that took in homeless orphans as 'children of Columbia.' That's why she could never simply accept that people with nowhere else to go should become sacrifices for someone else's future.

The job Maylander gave her was erasing the memories of agents whose missions were done. But this time, for the first time, she makes the opposite request — please, senior, whatever else you forget, don't forget how many lives and dreams lie behind that price.

8. Let's steal the whole park and run

Here, two rebellions erupt at once.

One is Gordon's. Instead of delivering his mentor's scripted 'apology speech,' he subdues Gustave with his modified robot Unit 054 and puts that face live on broadcast — kicking away the uncomfortable defendant's chair for good measure.

The other is Fen's. She leads the park's test pilots and company representatives in a charge toward the blockade line — calling out the names of their dreams, one by one. Rice Bush, Owen, Aspen...

Fen has a reason for going this far. Her father, Martin Van, never accomplished a thing and spent his days spinning nonsense tales for the neighborhood kids. For a long time, Fen was ashamed of him.

Only after he died did she understand what he meant by "a story is always more fun than an explanation." Never slapping the label 'impossible' onto a dream that hasn't come true yet — that was the one thing he left her.

Aspen too speaks his own name into the megaphone: swindled, chased by debt, left by his wife, and now a shopkeeper who's staked everything he has left in the name 'Lucky Kismet.' That was enough.

The plan is simple and reckless: gather up smuggled parts to build new engines, and U-turn the entire park right in front of the special district, then run it across the border.

9. The mother who became a tree

Meanwhile, Nasti finds Vayla inside the tree's roots — pale roots standing in for her legs, bark covering her face.

Watching the path back to Nasti collapse, Vayla had fused herself with the tree to keep that path alive — the tree sustaining her life, her keeping the tree moving. Like a program limping along, each propped up by the other's flaw.

Two hundred years ago, she'd said her burning, falling kin looked like kites with their strings cut. Now she herself thrashes, caught in countless roots and branches — like a kite tied to too many strings, unable to ever break free.

In truth, the Canyon's Roost Tree was nothing special — just ordinary lumber. It only became sacred because Vayla mourned and made it a symbol. There's only one reason Nasti planted a tree just like it in the sky: she missed her mother.

Nasti erases all the temporary data she'd loaded into the tree beforehand — so that Vayla can finally face, head-on, that the roars and curses tormenting her were really her own lingering attachment and grief.

And then she asks: what do you actually want to leave behind? This tree could become a resting place for departed souls to return to. What gets left behind at the end — this time, let's decide that ourselves.

Vayla agrees to become the tree's very first resident. "Just as I found you a home over twenty years ago, now you find one for me."

Her final memory, once every sorrow of the Canyon had faded away, was a single scene: a night, long ago, tucking in the child she'd just brought to the Canyon, telling her how adorable she was.

Nasti catches the falling leaf in her palm and blows across it. Because if it's just an accompaniment for a smile, you don't need a bone flute.

One tree left in an empty sky

In front of millions of citizens of the special district, the park falls in a blaze of glory — exactly as Maylander scripted, under the name of 'terrorism.'

But once the smoke clears from the empty sky, only one tree still floats above the clouds. Fowlbeasts are already preening their feathers on top of it.

Vice President Jackson could have defined that tree either as 'a victim of terrorism' or as 'Columbia's new symbol.' But a single word from Yara changes his mind — a memory of the mobile mining platform he'd chased after, skipping class as a young man, forever pursuing the sunset.

If that sky up there is the soil that will nurture Columbia's new age... then there's no reason we can't make room for one tree.

— Jackson

And so Rhine Lab stands at the door of a new era, confirming that all the ghost stories Christine left behind — the 'Star Gate' at the Infinite Ice Field, the Kjerag records, the disappearance at Black Flow — actually lead to a single answer.

The sky was always empty. What always filled it was people — merchants ruined by the craze, a guide who only chased the 'impossible,' and—

One mother tree, who chose to stay behind not in the Canyon but in the sky, not as grief but as laughter.