Chell has never run so fast in her life.

Wrench fastened to her back, she sprints down the alleyway with her boots crushing against cream colored cobble. Her diaphragm heaves with every sucking breath; her lungs ache with fire and exertion and sweat slicks down her neck and it feels like she can't go on because everything hurts, it hurts so much, but she has to, she has to, and so she ignores the pain in her legs and in her chest and she runs.

Ahead, the brick face of a building grows taller and taller at the end of her narrowing path. To her sides, the alley splits and veers off into other routes, but panic is a pair of wings behind her breastbone and all she can focus on is putting one foot in front of the other because she can't stop, she has to keep going, and her choices of escape dwindle with every step. She gasps in a surge of air as she spies an opening ahead to her left. Pressing a gloved hand to the alley wall, she hurls herself into the turn.

There is a moment in the twist of her flight where she can glimpse her pursuer. It has too many faces, too many teeth; steam gushes from its mouths and onyx claws gouge out chunks of cobblestone in its wake. It's been gaining on her since she left the Cabaret, leaping down the backstreets and hauling itself toward her with its midnight eyes and glinting metal hide.

It will catch her. There is no question. Machines can hunt without rest, and she will tire far before fuel will ever be a problem. She is only human. All she can do is run.

Chell lunges down the new path with her heart in her throat, but she doesn't know where it's taking her. She's never been on this side of Vaudeville. She could unsheathe her wrench and try to fight, but she's never fought one of these things, either. She doesn't even know what the hell it's doing here—this is a populated city of over three hundred thousand, full to bursting with inventors and scientists and technotinkers of all creeds and trades—someone should have seen it by now, someone, anyone—it's tearing up the goddamn streets and it's going to kill her.

The sound of metal scraping against stone is a thunder in her ears. She can hear the grinding of its joints, its inner clockwork, the gears churning and the steam rushing through its vents, and she can only run. Her throat is dry; she can't swallow. Her eyes are damp, but she can't cry. The cocktail of adrenaline threading through her veins has overpowered the clambering fear that has harpooned itself through her ribs, and all she can do is run.

Chell rounds another corner, her boots skidding on the dusty cobble, and she powers through the pain that's eating at her calves and squeezing at her lungs. Her heartbeat is throbbing in her neck and she can feel sweat rolling down her temples, but all that matters is moving forward, running, escaping

"MECHNOMANCER!"

It's a fierce shout, echoing down the maze of alleyways. Chell jerks her head up to the rooftops in search of the owner of the voice. Squinting, she thinks she can see a shadow overhead through the sunlit glare, but it's too bright and the monster is right behind her and if she spares a second to take a better look she will become a smear on the ground because it will kill her if she ever stops running.

She's halfway down to another turn when something flashes on the outskirts of her vision. A figure leaps out from somewhere above, sailing downward to her at an alarming rate.

On instinct, Chell dives into a roll. The ground strikes her shoulder as she spins onto her back, the wrench digging into her spine. She pushes herself up with the remaining strength in her arms, poised on the balls of her feet, her coat-ends brushing stone. One hand stays flat to the ground while she whips the other up to fasten to her wrench's handle.

Something lands behind her with a resounding crash that ripples her marrow. The cobble crushes beneath its weight and gives way to a broken crater and a flurry of dust and pebbles. As the breeze starts to clear the path, all she can think is that it's another one of the mechanical beasts, she's going to die, it's brought its friends, it's come to get her, she's going to die—

Chell unsheathes her wrench. It's heavy, half her height, and forged from a chrome alloy. She rises to her feet, gripping its handle in both hands. If she's going to die, if she's really going to be hunted down like human prey and torn apart by some malfunctioning machine, she refuses to die without a fight.

Through the clearing dust, she can discern the shape of a man. He's down on his knees with a black coat splayed about him in a furrowed semicircle. Just beyond, the creature seems to have paused in its pursuit. Mechanical jaws open and close, releasing jets of steam, and the creature's serpentine tail swishes back and forth with a structure that eerily resembles a spine.

The man peers over his shoulder. A shock of pink hair catches her eye.

"You'd best get down."

Without hesitation, Chell hits the ground.

Not even a moment passes before the screeching of the beast can be heard. Its claws strike stone, heads thrashing, and the weight of its movement sends a tremor beneath her. She grips her wrench and grits her teeth when she hears the sharp sound of metal on metal. Prickles trickle down her neck and gooseflesh engulfs her arms as the shriek pierces the air.

And then there's an exhale of steam, and she can feel its giant body collapse.

Footsteps approach her, measured and purposeful. When she opens her eyes, she looks up to see the man standing over her, clad in a pair of pinstripe slacks and matching vest. His long overcoat nearly touches his neat black dress shoes, fluttering in the breeze inches from her nose.

"Greetings," he says, the sun haloing the vibrant pink of his hair. He brushes a fleck of dirt from his lapel with a lazy swipe. "My given name is Thaddeus. It's fortunate that I found you. That chimera would have torn you to shreds. Or crushed you. Or burnt you. A very poor survival rate for encountering one of those, if any at all. I calculate three point four seven percent."

Chell leans forward, peering past his legs. The chimera is a sparking heap, a giant gaping hole through its hull. Its heads rest on the ground, etched in the likeness of lions, goats, and snakes. How the hell did he—?

"It has been permanently disabled," Thaddeus assures. Swooping down into a kneel, he offers his hand to her. "You're safe. No others have been reported in the area. It is a known fact that they generally do not wish to be seen. It is an anomaly to see them in the city, however. A total of three units have been sighted within Vaudeville's limits the past two years."

As Chell places her hand in his, she realizes that this man is not a man at all. His fingers are copper, hinged at every joint, glinting in the sunlight; even with her wrench in one hand, he lifts her to her feet with little effort. His face is copper as well, she notes; his cheeks are burnished and glittering, and the irises of his eyes are a brilliant pink to match his hair.

"My Maker has summoned you." Thaddeus gives a short and formal bow, his shaggy hair whisking into his eyes. "A business proposition. I don't know the details, but it's a ninety-one point three six percent chance it's concerning our newest addition. It's said he is broken. I do not have sufficient data to determine the validity of that statement, so I will abstain from setting that value."

Thaddeus extends one hand. In it is a folded envelope, sealed with a stamped blot of blue wax.

"Will you agree to attend my Maker in his office this afternoon?"

Chell accepts the envelope. She tears it open with one finger and glances over the letter inside. It's a short note, written in a cursive script on a crisp slip of parchment:

"Salutations, lucky invitee!

You have been chosen by our very selective team to participate in a lucrative business venture sponsored by Aperture Science and Alchemy. Should you choose to accept this invitation, the automaton accompanying this letter will guide you to our humble guildhall in Vaudeville's Tinkertown district where we can discuss this further.

We look forward to meeting you!

- Cave Johnson, Aperture Science & Alchemy Guildmaster and CEO"

Chell eyes the inked logo at the bottom of the note. So, it really is a formal invitation. She folds the parchment in half and tucks it into her coat pocket. Why would someone go out of their way to find her for something like this? She's not a part of any guild and she's been nothing but a wanderer, travelling from one place to the next in search of work. This is only her fourth visit to Vaudeville. It doesn't make any sense.

Her gaze shifts to the remains of the chimera among the cobblestone. The hole in its body is a straight shot from one end to the other; oil and pieces of its clockwork innards have spilled out onto the street. She has no idea how Thaddeus knew of its presence or even how he managed to destroy it so completely. The automaton didn't even look armed.

"Your response," prompts Thaddeus.

Chell hesitates a moment before she gives him a curt nod.

"My Maker will provide any necessary details of the proposition upon arrival," he says, offering her his arm. "I will be your escort. Considering your previous company, I am ninety-six point three five percent certain my Maker was correct in sending me."

Chell sets her wrench back into its clasp on her back. She doesn't know why she was being chased by a chimera or why someone at Aperture has suddenly become interested in her, but she has every intention of finding out. Dusting the dirt off of her breeches, she laces her arm with Thaddeus's and lets him guide the way.

"We'll be heading to Tinkertown," he says, leading her down the alley. "I would carry you, but my Maker has advised me against inappropriate travel decisions. He says it's upsetting to humans. With my superior engineering, I find I can travel far faster than organic beings—one hundred fifty-two point six three percent faster, to be exact—but at his behest, we will take the trolley."

Thaddeus navigates the narrow pathways, traversing the twists and turns and bins of broken parts and rubbish. They eventually emerge onto a congested street, the drone of steam-driven automobiles overpowering the din of the crowd. As they pass various fruit stands and meat shops on the orange cobbled sidewalks, Chell starts to notice something peculiar: the shoppers, vendors, and idling passersby seem very aware of Thaddeus's presence. When she draws close with the automaton on her arm, others step aside without hesitation.

"This is Wyck Avenue," says Thaddeus, gesturing with his free hand. "We're on the main strip of the commerce in Vaudeville, excluding Tinkertown. This road was constructed thirty-one years ago, and was named after Guildmaster Walter Wyck, the primary figure in the effort to secure trade routes between Vaudeville and Tiverton. That route was established in 1853."

Chell is less interested in Thaddeus's history lesson and far more interested in how everyone reacts to him. The more she watches others struggle to get out of his way, the more she tries to remember her previous visits to Vaudeville. With the time she spent hanging around mechanics, engineers, pot shops, and warehouses filled with parts, she heard a great deal about the guilds that called Vaudeville home. Aperture Science and Alchemy had been a prominent name, of course, but she's starting to think she hadn't realized the depth of its power. And the way Thaddeus had dispatched that chimera…

"The trolley stop is just ahead," he says. "The travel time to Tinkertown is seventeen minutes and forty seconds from here if the trolley is on schedule."

Chell glances across the street. A throng of people were standing under the overhang, and those that could not fit were gathered around the trolley sign. The crosswalks to get over were hit and miss; she found out very quickly that automobile drivers in Vaudeville tended not to care whether or not pedestrians were present.

She then gazes over to Thaddeus. He's paused his steps, staring down at her with a cocked head. His copper skin glitters under the late-morning sunlight, his flare of synthetic pink hair framing smooth cheeks and a pointed chin. His eyes do not blink, she notes; they are unnervingly still and focused, and they seem to emit a soft glow in the shadows of the nearby shops.

"Is there something wrong?" he asks.

"Carry me."

The corner of Thaddeus's mouth forms a smirk as if he's known all along. "Understood."

The automaton unhooks his arm from hers. Lowering himself, he presses his hands against stone and bends his back forward. His coat flutters against the ground.

"Fasten your arms around my neck," he says.

Chell does as she's told. The metal beneath her fingers is warm—from the boiler, she supposes—and she clasps her hands over one another around the thick of his throat. She feels the pressure of his arms wrapping around her legs and tugging them forward. Then, after he's sure she has been secured, he rises up to his full height. Others in the street are staring, she realizes, but it doesn't matter.

"Our travel time will be four minutes and fifty-eight seconds," says Thaddeus. "Time me."

Chell's heart lunges into her mouth when he leaps into the air. The crowds meld into indiscriminate colors and the noise drops from her ears. The rooftops race up to meet her and then she can see the tops of buildings, towers, and the streets become intricate mosaics below. An airship purrs somewhere overhead; she's afraid to look up, but she does, and she immediately regrets it because another ten feet and she might touch its hull. Thaddeus's pink hair is in her face and she can't breathe because she is so far above the ground, she's never been so high, and she wants to scream but her voice is a sharp shard down her throat and so she grips onto him and grits her teeth and tries to trap the sensation of flight inside her ribs.

"Going down!" shouts Thaddeus—and they go down.

He crashes hard into a rooftop, the aftershock shaking through her bones. She doesn't have time to see if he's left any damage in his wake; he's sprinting now, bounding from roof to roof in mere seconds, wind rippling past and sunglare in his hair. Chell has no idea how he's moving so fast, it shouldn't be possible, but it must be because he's clearing ridiculous amounts of distance with no effort at all—how, that's insane—and all she can think of is what if the chimeras could do this, what if that one was toying with her, what if it could have killed her and it was just wearing her out because why not, and Chell just digs her nails into the flesh of her wrists and hopes to god she's wrong.

Structures and buildings whip past. Thaddeus dives across another gap in the roofs, and Chell can glimpse the bronze and copper plated locomotives chugging in the streets below. With a hard swallow, she forces herself to look ahead. The north side of city slopes upward with Tinkertown at its apex. In the distance, the district's signature blue-gold clocktower rises up from the hillside, its gears slowly ticking. If she strains through the clack of Thaddeus's footsteps and the swish of wind in her ears, Chell can hear the tower chime as the clock strikes twelve.

The automaton continues his neck-breaking pace without missing a beat. There is still the twisting feeling of I'm going to fall tucked under her heart every time he makes a jump, but his hands grip her calves with rigid strength and she feels better with Tinkertown in sight. She takes a shaky breath, inhaling the scent of his hair and the musk of his collar and the perfume of the city below, and the longer he goes without dropping her, the more comfortable she feels.

When the clocktower draws close, she finds herself relaxed enough to admire the architecture of the various buildings as they pass. She's never exactly found herself in a position to view Vaudeville from such an angle, so she watches the arched and steepled rooftops plated with clay and stone shingles; she watches the great metal pipes snaking from place to place, carrying water from one part of the city to the other; she watches the various decorative bronze and brass trinkets that adorn windowsills and doorsteps; she watches Tinkertown engulf her and its clocktower spear up into the cloudless sky.

After they pass the tower's shadow and reach Tinkertown's center, Thaddeus leaps from the rooftops and descends into the street. Her heart flies up into her throat, but the landing doesn't faze her. Instead, she focuses on the surrounding shops and signs, advertising parts and inventions and handheld miracles, and a part of her wants to stop and poke through a few establishments to see if she can find any upgrades for her wrench.

Thaddeus bounds upward again, clearing a colossal metal fence. Ahead is a grand mansion with spiraling spires, ornate gardens, and stoneworked gargoyles guarding the roofs; a place Chell can only assume to be Aperture's modest guildhall. They must be far wealthier than she had imagined.

The automaton finally comes to a halt when they reach the mansion's front doors. He kneels down onto the stone steps and gently lets her legs go. She unclasps her hands from about his neck and slides off his back, somewhat grateful to be on the ground again.

"My Maker is waiting within," says Thaddeus. "I hope the chosen method of transportation was not too upsetting. And I thought you would be interested to know: our travel time was a total of four minutes and fifty-two seconds."

Chell can only grin.

Acknowledging her response with a nod, Thaddeus presses a small button to the side of the gigantic pine doors. A series of cheery chimes can be heard from somewhere inside, playing out some unknown melody. After a few moments, one door swings slowly inward, and another automaton peers out. It's rather diminutive in stature, much more than Thaddeus, and it reminds Chell of a child.

"Oh, who's that?" it asks, inspecting her from the safety of the doorway. Fiery synthetic hair curls up by its copper cheeks, coupled with striking orange eyes.

"This is our Maker's guest," says Thaddeus, placing a hand on Chell's shoulder. "Curie, please let him know she has arrived."

The little automaton nods and darts away without another word.

"That was Curie," says Thaddeus, leading Chell inside. "Forgive her if she does not remember you after this encounter. She has an unfortunate memory leak that prevents her from retaining information properly. She asks a lot of questions."

The entrance hall is a grand thing to behold. The floor is a glistening white marble, veined with streaks of black. Matching staircases rise up to a balcony overlooking the foyer and thick marble columns decorate each side. Floor-length windows line the walls and a skylight opens above, letting in the afternoon sun filter in to create great ponds of golden light on the floor.

In the center of the room below the balcony, a man stands with his hands folded behind his back. He wears a nicely pressed brown suit, she notes, and she can see his light brown hair flecked with salt and pepper, cropped away by his fierce widow's peak.

"Welcome to Aperture Science and Alchemy," says the man, his voice echoing about the giant chamber. It has an unnatural strength to it, but she can see from the color of his skin and the wrinkles in his face that he's no automaton. "I see you've already met Thaddeus on the way over, so let me introduce myself."

He approaches Chell with steady steps. He pauses before her, right hand extended, mouth pulled into a wide grin.

"I'm Cave Johnson. I own the place. And if you're the lady I think you are, I've got a job for you."