Irini lies awake as her mother sits beside her on the mattress and strokes her hair, but she keeps her eyes closed in feigned sleep so that she can keep listening to the song her mother whisper-sings in the alien tongue she only speaks when she thinks no one else can hear. Irini doesn’t yet know that in six years her mother will be cast back out of this world and trapped beyond the Portal. She snuggles into the covers, smiling, comforted by the sound of whirring gears and the pneumatic wheezes of the Clockwork Guards outside her bedroom door, never dreaming that they’re not clockwork at all, those strange-faced beings still concealed in their hydraulic suits—that they are biding their time and one day, six years from tonight, they will attack her family and drive them out before they come for her.

At this moment, there is only one path through the maze of her life, and it runs in a straight line from the temporary safety of her childhood bed to the hour she flees the palace in desperation and fear.

Then, in a blink, she is years farther through the maze, and here near the end there are multiple paths, each a possible life, and she lives all of them.

In one, she has returned to the Park of Future Heroes, to defend her native city and defeat the Clockwork Guards once and for all. She looks up and sees the chiseled likeness of her own face gazing down from the carved stone majesty of the statue known as the Defender, until she hears footsteps and the clatter of armor behind her. She turns to confront the Imperator, the former Captain of the Guards, as she slides her sword from its scabbard for the final battle.

But now she is on a parallel path, and the Defender statue lifting its sword in this timeline bears the Imperator’s tentacled maw. The Usurper, the cowering traitor awaiting his blow, wears Irini’s face. This time, when she steps out onto the grass, her muscles clench when the Imperator strides up to face her. When he lifts his blade, a smaller replica of the weapon wielded by the statue behind him, Irini wants to run, because the statues reveal to her how this will end. But she stands her ground and raises her own steel, her hands steadied by years of training. The Imperator’s blade hacks away her parry and strikes up and across to chop into her neck. As the steel slashes her windpipe, she slips quickly into a different moment of an alternate life.

Irini wanders the labyrinth of her past and future memories, all the simultaneous futures and histories. But there is a chokehold, a single point, between the linear thread with which her life began and the coiling strands through which it multiplies and eventually, in various guises, ends; and this knot is a particular night in the Park of Future Heroes. This is the night her family is betrayed by the Guards, and this betrayal is the beginning of the multiplicity of nows. So she returns to that night, and in this now she is running.

She races to the only place she knows to hide: the Park of Future Heroes. Her feet are sore from her heels slapping the paving stones through her ornamental sandals, her skin is hot and the air is icy against it. She rushes into the park, gasping for breath with her chest heaving, and leans her back against the looming Clocktower. Through the cold, ancient, weathered stones she hears the clicking of gears. Then a figure appears out of the darkness before her. Her heart jumps to her throat. Irini knows this girl.

“Princess Irini,” Cheri says, looking at her directly. She’s just a few years older than Irini. Everything about her is a challenge to the decorous palace life Irini has just left behind, from the unrestrained gold-brown mane of her hair to her bold green eyes. “Don’t worry. The Palace Guards won’t find you here.”

“How do you know they’re after me?” Even through her shock and disorientation, Irini is sure as soon as she blurts out the question that it was a mistake. She shouldn’t be admitting that the Guards are seeking her to the park’s caretaker.

“I’ve been waiting for you.”

Irini has a sensation of the world narrowing and closing all around her, until everything is focused on her and the girl in front of her in this shadowed park. The clicking gears behind her begin to sound loud and relentless. She steps away from the tower, but that only brings her closer to Cheri and her penetrating eyes.

“I can help you escape them,” Cheri says.

Irini stiffens.

“I can see possible futures,” Cheri tells her. “In every one of them, the Guards chased your family through the Portal and came for you. I knew you would end up here.”

Irini looks up at the five statues in their well-known poses, undefined figures carved from rough stone, deliberately unfinished, their hands outstretched or clenched in fists, their faces blank on featureless heads. The Defender, the Usurper, and the Warriors, their identities still to be chipped and incised into view.

“I have to go,” Irini says. “If I leave the city, they won’t find me.”

“You can’t get your family back. But you can stop the Guards.”

Irini flinches. “How do you—”

“I told you. I see possibilities.”

“Can you get me out of the city?” Until I can figure out how to get back and reopen the Portal.

Cheri is silent for a long moment. “Yes. But it’s not safe right now. They’re out there looking for you. Let me hide you first.”

From beyond the arched gate, Irini hears the clank and wheeze of the Guards’ armor. She looks at Cheri and nods.

Cheri places her palm against one of the Clocktower’s bricks and pushes. There is a grinding, scraping sound as a concealed door separates from the wall and swings inward.

Irini walks to the doorway and hesitates. Would Cheri trap her to ingratiate herself to the kingdom’s new rulers?

But certain doom is more urgent than the theoretical kind, so Irini follows her through.

She steps into darkness. The perfumes of the city, salty bay air and night-blooming flowers, mixed with the stink of trash in the street, are replaced with the sharp, biting scents of oil and metal and stone. “I never knew there was a way inside.”

“There is much you and your family don’t know of our world,” Cheri says. Springs pull the door shut again behind them, sealing the girls in shadow. Now Irini can see pale strips of moonlight cast at regular intervals through chinks between the bricks. “You’re strangers here.”

“I was born here,” Irini says.

“Even so. The conquerors don’t need to learn the ways of the conquered.”

Irini’s face burns, but she doesn’t know what to say as she follows the older girl up a steep, narrow stairway. Her eyes fix on the rise and fall of the heels of Cheri’s leather boots. Rough stone scrapes her elbow as she follows the stairway’s curve. The ticks of mighty gears echo through the walls.

“My family are the clock’s caretakers,” Cheri says finally, more gently, as if apologizing for her cold tone earlier.

“Where are they?”

There’s another long pause, and for a moment Irini wonders whether Cheri heard her over the ticking. “It’s just me now.”

Irini climbs for another minute. They’ve probably reached the level of the lowest of the fourteen clock faces. Irini is still struggling with a response over Cheri’s accusation that she’s a conqueror when Cheri speaks again. “This tower is connected to the engines in the heart of the world. Did you know that?”

Now she’s just trying to prove Irini’s ignorance. Irini doesn’t respond. “Do you know why you came to Misith?”

“I told you. I was born here.” Irini is out of breath and angry and the words come out as a hiss.

“You wanted our secrets. So you could open the gates between worlds.”

Irini grinds her teeth against a retort. She doesn’t have to defend herself to Cheri.

The two of them reach a hardwood landing near what must be the top of the tower. Another flight of steps ascends through an opening in the ceiling. Cheri leads Irini past a closed door to an embrasure that looks down onto the park below. Through it Irini can see that the area they just left is filled with Guards.

“They must be using the park as a base to scout the surrounding streets,” Cheri observes. Irini watches as several Guards leave her field of view while others appear, reporting to a lieutenant positioned next to one of the Unknown Warriors. Then she raises her eyes to the caretaker.

“Why are you helping me?” she demands. “Why do you care?”

Cheri keeps her gaze on the scene below. “We have the same enemies. The Guards killed my parents.”

“They ...” Irini shakes her head. “I’m sorry. Why?”

“They were your Guards. Why do you think?”

“How would I know?”

Cheri straightens and turns to Irini. “You don’t know what the Guards did in your name?”

Irini’s cheeks grow warm again. “They were there to protect us inside the palace. That’s all.”

Cheri narrows her emerald eyes. “Well, now you know they’re your enemies, too. And you can return the favor. You can help me.”

Finally. Through Irini’s frustration and fear and grudging gratitude she can finally find out what Cheri really wants, and what she’s gotten herself into. “Help you how?”

“In the palace is the Portal the Guards opened to come to this world.” “Not just the Guards. My parents.”

Cheri nods in satisfaction, as if this is an admission. “Your family thought the Guards came to protect you, but they were just seizing the opportunity. The Guards needed your family to find their way here, and your family needed the Guards’ strength to remain.”

Irini wants to ask how she knows the Guards’ thoughts, but she already knows what she’ll say. Cheri sees possibilities, and some of those eventualities must reveal the Guards’ intentions.

“All this time their allies have been building reinforcements on the other side, and someday they will march here in their hundreds of thousands. That’s what the Future Heroes will protect us against. But even though the custodians can see probabilities, we can’t know which side will win.”

Irini glances back down through the embrasure. She sees two Guards standing below, staring at the tower. The lieutenant is no longer visible.

“We can stop them,” Cheri says. “The Portal can be sealed from this Tower, and the lock can be broken so it can never be reopened. If you help me.”

“My mom and dad are on the other side!” Irini realizes, too late, that she’s raised her voice. One of the Guards below looks up and says something to his companion. Is it a coincidence? Has he heard Irini through the opening, above the ticking clockwork?

Cheri looks at Irini with a careful expression. “They’re gone,” she says softly. “Your parents aren’t coming back. But you can help me save the world.”

Irini locks her jaw. She’s not going to help Cheri. But it’s probably not a good idea to announce that.

There’s a loud boom below them. After a moment, the sound is repeated: a heavy thud that reverberates through the walls. Cheri looks down.

“They’ve found the door. They’re trying to get in.”

“Can they?”

Cheri shrugs. The boom comes again. “No one’s tried to force their way in before.” She heads to the stairway up. “We have to hurry.”

“Is there another way out?”

“No.”

Irini heads to the closed door instead. “What’s through here?”

“Irini,” Cheri insists, “I need your help. If you can cut the connection while the Portal is being sealed or unsealed, it’s like breaking a key in the lock.”

“Princess Irini,” Irini corrects her. She looks away immediately, disgusted with herself for pulling a rank she’s always felt as a burden but not willing to let Cheri see her weakness. She strides to the door and pulls the handle. It yields, and the door swings open.

The next boom from below is followed by the sound of splintering wood and brick. An instant later, Irini hears the wheezing, clanging sounds of Guards stomping into the tower. Cheri growls out her fear and frustration and races up the steps. Irini steps through the doorway.

In a small chamber of bare brick stands a stone pedestal, the same ash-gray marble that forms the unfinished statues outside, supporting a globe of polished brass. Irini’s indistinct reflection grows and warps across its surface as she approaches. Her hands are pulled to it, like iron to a magnet, and as soon as her fingertips touch the cold metal she is plunged into the stream of probabilities.

The single stream branches and those branches further divide. All the branches have the same beginning: after she leaves this room she follows Cheri up the steps. She finds her on the next and highest story, in front of a panel of wheels and levers, pulling back one of the levers with both hands. Rows of mirrors capture and amplify the moonlight. “I’m locking the Portal,” Cheri announces above the clicking of gears. “Go down and break the connection below.”

Irini follows the direction of her gaze to a hole in the center of the floor. She steps to the edge and lurches back in vertigo. The hole encompasses the machinery that fills the center of the tower and dives down, down, past the ground, into impenetrable darkness, possibly all the way to the vast engines at the incomprehensibly deeply-buried heart of the planet itself.

Then Irini takes a breath and jumps. Her stomach seems to flip inside her. She catches the outer edge of a horizontal gear wheel, one of a pair of bevel gears, with a diameter as long as she is tall. She grabs on as she slips down its angled side until its sharp teeth bite into her palms. The gearwheel flings her out as it turns, and she tucks in her legs to avoid having them amputated by a passing pendulum. The wheel brings her around to its vertical partner, and before she can be chewed up where they mesh, she throws herself into the air—

—past another pair of meshing gears—

—and onto a pendulum just starting its ascent. She clings with her legs and arms wrapped around the metal rod, rising and falling along the arc of its swing. Soon Cheri will follow, and Irini will jump and clamber up to join her on the spindle of a rotating horizontal wheel. They will spend more than a day huddled down here together, shivering with cold and exhaustion and hunger. In only one of the possible branching futures do the Guards discover them before they finally dare to climb back up onto the top floor. In some of the futures, Irini tries to convince Cheri that she attempted to break the connection to the Portal and failed. But in every future in which they escape the Guards, Cheri at least suspects that Irini refused to save her world. She must have known in advance what the outcome was going to be, and in her desperation she reached out to Irini anyway. In each of these futures, Irini leaves the tower alone.

Irini blinks and she is near the end of the maze again, back in the Park of Future Heroes in the doomed role of the Usurper. This time, though, something is different. When the Imperator marches out to meet her in the shadow of the statues, two pale creatures shuffle beside him. They look like bloated ticks, each the size of a pony, encased in shell-like armor. They screech and hurl themselves at Irini before she can take out her sword.

It’s not possible, the part of her watching from the tower chamber thinks in the moment before she dies. This is a possible future she’s already experienced, but the tick-things weren’t there. How can any creature invade and change possibilities?

Have the Guards found a creature that can cross possible timelines, in one of the dozens of worlds the Portal can potentially access?

Now she is back in the Park as the Defender. She turns and draws her blade as the Imperator appears, confident of her victory. She hears the now-recognizable shrieks before she sees them: three of the armored ticks scuttling forward beside her familiar enemy. Their capitula stretch wide to extend sharp feeding tubes. Bulbous eyes on their sides seem to see her, through her—not just the woman in this now facing inevitable death, but the girl still standing in the tower. They will come. They will find her, they will chase her, through any alternate timeline.

Back in the tower, the surge of probabilities hits her like an electric shock and she staggers back. Her fingers release the orb. In the fraction of a heartbeat her skin was in contact with the metal, she lived dozens of multiple lives.

She hears the heavy thud of boots as the Guards begin to mount the stairs at the entrance to the tower far below.

She exits the chamber and bounds up the steps to Cheri. Now she knows the army waiting on the other side of the Portal is more diverse and powerful than she could have imagined. But she also knows that she never needs to come here to the capital again, except to return to the Portal itself. Someone else can be the Defender. As Cheri has reminded her, this isn’t her world. The statues are still uncarved.

In the maze of alternate futures, there are times when the Portal reopens and her family steps through. Her parents and sister are there and they love her. It’s a possibility that exists. She doesn’t need to defend Misith to reach it. Maybe, if the future possibilities are somehow changing, she can only reach it if she doesn’t.

Cheri is where Irini knew she’d find her, on the next and highest story, in front of a panel of wheels and levers, pulling back on one of the levers with both hands. “I’m locking the Portal,” she announces above the clicking of gears. “Go down and break the connection below.”

Irini jumps down and catches the bezel gear. As she swings around, she looks up and sees a rod connected to machinery suspended from the ceiling above. It looks like a simple, mechanical connection, but she knows from the many lives she’s just lived that it’s a conduit for the elemental forces that keep the Portal intact.

Her mind returns to the Imperator and its scuttling companions. They are waiting. Whether she is here to stop them or not, they are waiting. She retracts her legs to avoid a pendulum and then kicks them out with all her force. Her sandaled heels hit the Portal rod and it shudders. She kicks again and feels the snap as it breaks free of whatever held it tight down in the darkness. Then she jumps to another pendulum shaft before she can be ground into meat by the bezel gears.

For the first time since the Guards attacked Irini’s family, she smiles. The Portal is broken. This is the one action she never took in any of the futures she’s just seen, and that means she has no idea what will happen next.