A siren blares around him as Dean stumbles through the hallways, head ringing from the savage shock to his skull. He thinks he can hear the voice of the station's mother, tinny and repetitive as it grates on his eardrums. " Orbital stabilisers compromised. Attempting recalibration."

That's the second devastating blast the stabilisers have taken. They won't survive a third.

It's hard to even tell where he is. He's in an unfamiliar part of the station, and any signposting there might have been is lost on him as he tries to stay upright, barely able to focus on the path immediately up ahead.

A slightly higher pitched automated voice overrides the first, the two competing to make their infuriatingly calm announcements over the decidedly not-calm alarm. " Air seal compromised. For your safety, the docking bay has been placed in automatic lockdown."

No going back that way, then. Dean's not sure he could even find his way back if he tried. Something else is on fire, and he begins to cough violently as he starts to choke on the smoke. The station's still rocking, trying to find its centre of gravity, and he throws his hands out to clutch at the wall. He needs to get back to the lower decks, somehow. There has to be an elevator. Even if it's offline, it would be a start.

The gravity shifts again, and Dean takes several stumbling steps sideways. Maybe it's that he missed his footing, or it's just that the station is falling apart, but the next thing he knows is that something has given away beneath him and his stomach flips as he find himself dropping into an open shaft.

Panic instincts kick in. His hands flail, scrabbling at the smooth metal sides for something to grab onto, legs kicking, sending jarring shocks to his knees and ankles.

He can only have been falling for three seconds. Less.

"Dean!"

A tight grip closes on his right arm. He gasps, pain tearing through his right shoulder as it halts his fall, and then he cranes his neck up. "Cas?"

The WY rep stares down at him from the shaft's opening, then, with surprising strength, lifts him smoothly one-handed back to the top. Dean scrambles over the side, and barely has time to manage a "What…?" before he hears another voice, overcome with relief as a smaller body throws its arms around him.

"Dean!"

"Sammy?" The surprise hasn't quite worn off before Dean returns the embrace, wrapping his brother tightly in a hug.

"I thought Henriksen had blasted you into space."

"Sorry, kiddo. You aren't getting rid of me that easily."

Over Sam's shoulder, Dean blinks at Cas. The older man is watching them with an unreadable expression on his face. "What...what are you doing here?"

"We have to stop the synthetics," Castiel says, as if that answers anything. "They were on a rampage. Sam and I were making our way to the AI station when we saw the Anesidora undock."

"I knew that was you," Sam says, finally pulling away. "I knew you couldn't be dead."

Dean swallows. "Actually, it was Anna."

He's about to say something else when the alarm suddenly stops blaring and the rocking of the ship evens out. There's a beat, followed up by an announcement, " Orbital stabilisers recalibrated. "

The sudden steadiness of the ground is a relief. "Crowley escaped and tried to blow up the station. Anna stopped him," Dean tries to explain as succinctly as possible, then shakes his head. "Wait, what do you mean 'stop the synthetics'? How?"

"Dean," Sam says, and he sounds inexplicably excited. "Cas is a synthetic!"

" What?" Suddenly, Dean is straightening up, backing away from Cas and grabbing Sam's shoulder to drag him with him. He eyes Cas warily, fear and suspicion painted plain on his face. "What the hell, man?"

Castiel eyes him calmly. "Dean, you have nothing to fear from me. I'm a Weyland-Yutani model, not Seegson. I have none of their programming."

"Dean!" Sam protests, shrugging off the grip on his shoulder and trying to move towards Cas again. "It's alright. Cas saved my life. One of the Working Joes tried to kill me and Cas stopped it. He's on our side."

"Yeah," Dean says, voice cold. "Thing is, Seegson synthetic or not, you lied." He fixes Cas with a glare.

"I didn't lie. I...merely neglected to inform," Cas defends, and it only makes Dean trust him less. "At the time, it didn't seem necessary."

"Oh, right, not lying," Dean says. "So is there anything else you neglected to inform us about? Because I had an interesting conversation with Anna before she died. She told me she knew about the creature when she was sent here. Weyland-Yutani thought they could use it or something for weapons development, so that was the real reason she came. My mom was just the pretense. Did you know about that too, Cas? Was that in your programming?" He fixes Cas with a glare.

The android stares back in silence, eyes flickering down. If Dean didn't know any better, he'd say he almost looks guilty. "I knew," Castiel confesses. "But I've come to realise that what Weyland-Yutani want is wrong. Since I've been here, I've seen what that creature can do. People are dead, and more people will die unless I do something to stop it. Something in this station's AI is programmed to protect the xenomorph and has shut off possible routes for the humans on board to escape. Only I can stop it, and I will do whatever I can to protect those are left."

He seems sincere. Genuinely. Dean wonders how the hell anybody could programme that. "Why? Doesn't that run counter to everything Weyland-Yutani have programmed you to do?"

A small smile curves on Cas' lips. "Maybe I'm more human than you give me credit for."

There's silence for a beat, Dean frowning as he tries to figure out what to think. His head is telling him not to trust an AI, but his instincts are saying something else.

"Dean," Sam says again. "It's alright. He saved my life. We can trust him."

How that would fit in with any agenda to protect the creature with all humans considered expendable, Dean can't tell. And anyone who protects his little brother is good in his book. "Alright," Dean finally relents, and hopes he won't regret it. "You want to stop the Working Joes, I'm coming with you."

Cas nods, grateful. "We need to make it to station's central AI. The APOLLO interface is on deck 21," he says. "Be careful. If we encounter any of the Working Joes, they will try to stop us."

"Not to mention the xenomorph," Dean says grimly. "We failed on that. It's still here."

"Then let's hope it keeps to its own part of the station," Castiel says, and nods down the hallway in the direction of a hatch with a ladder. "This way."


They make it to deck 21 without running into any further Working Joes or encountering the xenomorph. The hatch brings them out at almost the very top of the station, onto a hallway branching off in three directions. Down one route Dean can see the inky black of the sky outside peppered with stars, through the glass dome of an observation hatch. Another route leads along a hallway with padded walls towards a vertically sliding door. Dean recognises the design. "That's the station's Mother…" He's begun to take a step towards it, but Castiel puts a hand on his shoulder to stop him.

"That's the human interface," Cas says. "The AI interface for APOLLO is this way." They take the final route towards the door labelled " Seegson APOLLO", which Cas opens with a touch to the handprint scanner beside the lock. "It only responds synthetics," he explains as the doors slide open and Sam and Dean follow him through.

The room beyond is a control center, a console full of blinking lights in front of a glass screen looking out onto the main interface. If Dean had to describe the machine he can see beyond the safety screen, he'd say it's basically an MRI scanner with the word "APOLLO" emblazoned down the side.

"That's where I have to go," Cas says, looking out at it. "A synthetic in the chamber can interface directly with the station's AI. I'll get it to shut down all active Working Joes on board and reopen the comms channels, but it isn't going to like it." He crosses to the console and powers on some of the controls.

"I'll do my best to interrogate it on the creature. There will be a power surge," Cas says as he pulls open a cover to reveal the circuit breaker. "APOLLO has defense mechanisms programmed in. It will try to keep me out. If these breakers blow, keep switching them back to ON no matter what happens. If you lose one circuit completely, you need to rewire." He gestures to the glass-screened boxes stacked by the walls, through which Dean can see a myriad of multicolored wires tangled together and jacked into different ports. It's an artificial neural network center built on an industrial scale. "You're an engineer, Dean. I trust you can manage that."

That's a lot of pressure suddenly on his shoulders, and Dean swallows nervously. "I'm an engineering apprentice."

"Your father spoke very highly of your skills," Cas responds. "I have every faith you can do this."

That leaves Dean momentarily too stunned to speak as the feelings of pride and loss clash horribly inside him, then Cas is already at the door to the interface chamber. "It isn't safe for you to follow me through. Remain in this room no matter what." He shuts and bolts the door behind him, the heavy magnetic lock sliding into place.

Cas strides over to the machine and hits the button for the shelf to extend, which slides out slowly from the cylindrical chamber with a slow mechanical rumble. He lies himself down on it and adjusts his trenchcoat before laying his arms flat at his sides. "Sam, Dean," he says, and his voice now sounds tinny coming over the mics picking up his voice in the room. "The slider on the console will put me back in and activate the machine."

Sam finds it and pushes it into position, then as Cas vanishes into the chamber until only the soles of his feet are visible, lights flicker to life on the interface. An electronic hum begins to sounds from somewhere beneath their feet.

"I'm into the first level," Cas reports, voice calm. "It's granted me access, but it's going to get harder the deeper I go."

Dean watches the circuit breaker nervously. He exchanges a glance with Sam, who can hear the electrical hum grow loud.

Without warning, there's a flash of blue from inside the chamber. One of the circuits throws.

"Cas!" Dean cries out, worried, but the response he gets is calm.

"Keep going," Cas says as Dean resets the circuit. "I'm working on the firewall."

There's a few more seconds of the machine roaring, then Dean sees actual sparks fly from inside the chamber. "Shit!" He hurries to push the circuit breakers back on, worried what exactly it is he keeps overloading. One of them refuses to go.

"Sam, cover the switches," he says as he goes and tries to find which box has blown. The scent of burning plastic clues him in pretty fast. "Cas, what's going on?"

"Directive 314," Cas says, and his voice is turning more artificial. Robotic. "A Weyland-Yutani protocol was uploaded to the system in the last update shortly before we got here. It looks like a Trojan."

Sam's trying to stay on top of the overloading circuits while Dean reroutes one of the networks. Another one's just gone, and there's a thin stream of purplish smoke drifting out of the chamber. "What's directive 314?"

"I can't access the complete code, but I have the logs. The Working Joes were ordered to purge all human life on the station after it became a threat to Weyland-Yutani interests."

"Wait!" Dean shouts as he pushes a cable into a jack, and gets a sudden burst of sparks for his efforts. He hisses as it scorches his hand. "The rampage didn't start until after Henriksen jettisoned the ambulance. Wasn't it too late?"

Cas doesn't answer. There are more sparks, the brothers exchange worried glances, then he says. "There's more."

"More?"

No sooner has Dean said it, the box he's working on explodes. He lets out a cry, falling back as he tries to shield his face from the sparks. Sam rushes over to him. "Dean!"

An alarm begins to sound, a dispassionate female voice reciting. " Warning! System overload."

"I'm okay," Dean says shakily, picking himself up and stumbling back over to the console, Sam's arm under his shoulder. There's the red glow of flames from inside the machine now.

"APOLLO has detected more signs of alien life on board Sevastopol," Cas says, and his voice is almost too distorted to hear.

That makes Dean's blood run cold. "Shit, where?"

"I'm trying to locate it."

"What about the nest? In the morgue?"

"No. It's too small."

Too small. How many of the fucking things are there? Dean's mouth goes dry. "How can there be-"

He's cut off by the sound of another explosion, flames erupting from the interface while inside the control room, the lights flicker. Sam suddenly cries out. "Cas, that's enough! Get the hell out of there before the whole thing blows."

"I'm afraid I can't do that, Sam."

Dean sees the look of dread cross his brother's face. "What do you mean?"

"I need to disable the Working Joes and open the comms channels to allow you call for help," Cas says, and he still sounds calm despite the chaos. "I almost have it. If Captain Mills is still here, you will be able to contact her to evacuate."

"Cas, man, come on," Dean reiterates. "This thing is gonna kill you."

Castiel ignores that. "I lied about the flight recorder. I have the encryption key," he says. "BX3211J508. You should be able to access it by interfacing with Mother. I've installed an override in the system. Use my designation: Castiel-S4-12-PN."

Something else blows, and Dean suddenly finds himself dragging Sam back from the console to avoid electrocution. "Cas, it doesn't matter about any of that right now. Just get the hell out of there."

"I'm sorry, Dean. I…"

He doesn't finish the sentence. Everything descends into a garbled, electronic moan, and then he falls silent. The machine gives another roar, a final spark crackles through the smoke billowing from the chamber, then the electronic humming below them goes still. The alarm stops.

"Cas?" Dean says tentatively, then Sam shouts.

" Cas!"

As the smoke clears, they both squint to see what they can make out through the glass. The entrance to the interface is just about visible, a pair of feet still lying motionless on the shelf. White fluid drips down.

"Shit," Dean mutters, then pulls himself together. "Alright, Sammy, we need to go." He starts to drag Sam back over to the exit, trying to make sense of what they've just learned, by his brother struggles in protest.

"Wait! What about Cas? We need to get him out of there…"

"Sam, he's gone," Dean says forcefully, and hates the way his brother flinches. "I'm sorry. I'm sure Weyland-Yutani have him backed up somewhere, but there's nothing we can do." He pulls Sam over to the doors, relieved as they slide open automatically and then the brothers are stumbling back out into the clean air on the other side. They both look back briefly, horror plain on Sam's face while Dean appears to be in shock, then the doors slide closed and seal Cas' body away with it.

It takes a moment for Dean to collect himself. "We should do what he says," he eventually gets out, surprised by how shaken he is. "We can interface with Mother. Do you still have the box?"

Sam licks his lips and nods.

"Alright. Come on."

They make their way back down the corridor towards the Mother pod, reaching the door and then halting as they examine the lock by the wall. "It needs a key card," Sam says. "Even with Cas' override, we can't get this open."

"Yes we can," Dean says, remembering the ID card he'd taken from Dr Cortese. "Here. Found this." He takes it out of his pocket and pushes it into the slot. There's a pause, the lock beeps, then there's a hiss of hydraulics as the door slides up. Dean grins. "Told you. Come on."

They make their way inside, the near-spherical room small, but with every possible surface covered in controls or blinking lights. The chair in the center is only big enough for one, the computer and interface located right in front of it. Dean turns to Sam, who's taken the box out and has it clutched in his hand. "You, uh, remember the encryption key Cas said?" It was long, and they hadn't exactly been in a position to write things down.

"BX3211J508," Sam recites, and Dean raises an impressed eyebrow.

"You and your perfect memory."

"I just know good memory tricks, Dean. You should try them." He steps forward, takes the flight recorder and places it on top of the interface so that it lines up with the magnetic reader. "Okay. You think that should do it?"

"Let's find out." Dean takes a seat at chair in the center of the pod, Sam hovering over his shoulder as the lights blink around them. He clears his throat and looks at the screen. "Alright, let's try this. Mother, request clarification regarding directive 314."

There's a beep, then a series of clicks as the response appears on screen. Unable to clarify. Special clearance required.

Dean blinks. That was expected. "You remembered the designation Cas gave too?" he whispers to Sam.

His brother nods. "Emergency override. Authorization: Castiel-S4-12-PN," Sam says clearly.

The computer beeps, then accepts. Directive 314. Priority one. Preserve the creature at all costs. All other priorities rescinded. Crew and civilians expendable.

Dean swallows. "Well, shit." That's just chilling. He's still letting the sheer coldness of it sink it when Sam whispers in his ear.

"You think it can tell us more? Where the other aliens are?"

It's worth a shot. "Mother," Dean says. "Elaborate."

There's more beeping while they wait for the computer to load what appears to be a sizeable file, then more green text appears on the screen.

Message for: Milton, Anna

Re. Directive 314

CLASSIFIED

Primary objective: Retrieve data from the flight recorder of the USS Nostromo. If direct contact with the creature becomes possible, PROTECTING COMPANY ASSETS TAKES PRIORITY.

"They knew," Sam mutters as he reads. "They knew it was out here."

They continue down the page, Dean's stomach turning the more he sees.

Civilian casualties are rated as likely. Do not allow this to interfere with the prime objective.

" Holy fuck, the bastards. " Dean scrolls down, more green text appearing at the end of the briefing that makes his fists clench.

Re. John Winchester

It has been noted that John Winchester's personal endeavours while working for the company have brought him close to uncovering information about the creature. He has become a liability. Company interests would be best served by offering Winchester the opportunity to review the Nostromo's flight data first hand.

The truth settles on Dean like a dead weight, horror churning in the pit of his stomach. "They meant for this to happen," he whispers. "They wanted dad to come out here so the alien would kill him. Just like it killed mom."

Sam swallows. "And us?"

"No loose ends," Dean says, gritting his teeth. "They wanted us dead, too."

The two of them exchange a glance, both letting that sink in, then Sam says softly, "What about mom? Do you think...she knew? What the company had done?"

Dean glances down at the black box still plugged into Mother's interface and swallows. "I guess there's one way to find out." He opens the external drive menu and accesses the box.

Contents encrypted, the screen prompts. Enter password.

Dean allows Sam to lean over his shoulder to do it for him before it takes him to the home folder, split into Flight Logs and Crew Records. Dean accesses the flight logs first and selects the most recent audio: June 2122. Ten years ago.

"Play recording? Y/N" Mother asks.

Dean hits Y.

Final report of the commercial starship, Nostromo.

The audio begins, and both Dean and Sam feel a sudden unexpected jolt. They know that voice, painfully familiar even though they haven't heard in years. Sam's hand digs into Dean's shoulder, and Dean reaches up to rest his own over it.

Third officer reporting. The other members of the crew, Turner, Harvelle, Creaser, Murphy and Captain Singer are dead. Cargo and ship destroyed. I should reach the frontier in about six weeks. With a little luck, the network will pick me up.

This is Mary Winchester, last survivor of the Nostromo, signing off.

For a moment, there's silence. Dean licks his lips, struggling to process what he's just heard. "So, that was it," he says, numb. "Her last recording."

"No."

"No?"Dean blinks, looks up at his brother, and sees Sam swallow nervously.

"Check her personal folder."

He's right, Dean realises. With his hands not quite steady, he tabs back to the main menu and accesses Mary's folder under the crew logs. There's only one file, waiting for him to select, and he does so with his heart in his mouth.

The green message looks expectantly up at him from the screen. " Play personal recording? Y/N"

Dean turns to Sam. "Ready?"

The younger boy threads his fingers through Dean's and then nods, his expression solemn. "Ready."

Dean hits the "Y".

There's a pause as Mother beeps and clicks, and then the file begins to play.

This is Mary Winchester, the recording begins , and they both feel the same pang at the sound of her voice. Weyland-Yutani employee number 80368-572.

In the event of my death, please pass this message to my husband, John Winchester, and my sons, Sam and Dean.

Personal recording begins.

John, my love. There hasn't been a day I've spent out here that I haven't thought of you and our boys. You were always at the front of my mind, especially in the final moments when I didn't know if I would ever see you again. You'll know by now what happened to me, and if you're listening to this, it means I didn't make it back. My biggest regret is that I wasn't able to see you one last time to say goodbye.

I know you have questions. You must be wondering why I would choose to destroy the ship, choose to destroy my best chance of getting back to you, but know that it was a last resort. The creature I encountered out here can't be allowed to return to Earth. Even if it goes against all company orders, I had to stop it at any cost.

Sam, Dean, I miss you so much, my angels. I'm so sorry for all the time I missed, and the time we'll never get to spend together. No matter what happens, know that I am so, so proud of you and will always love you.

Please don't waste your lives being angry. I am angry at the company; angry at their deception and their disregard for the lives of my crew and so many others, but this isn't what I want for you. Do not go looking for revenge. Please live your lives, be happy, and stay as far from Weyland-Yutani as possible. I cannot allow them to hurt you the way they hurt me. Remember me, and let me go.

If it helps, know that in the end I defeated the creature, though it wasn't enough to bring me back to you.

Her voice hitches on the recording, breaks, and Dean feels a lump in his throat. He squeezes tight on Sam's hand.

I love you all so much.

This is Mary Winchester, last survivor… She pauses and corrects herself. Third officer of the Nostromo, saying goodbye.

Personal recording ends.

For several moments after the recording ends, there's silence. Dean turns to Sam, sees there's tears on his cheeks.

"So, that's the truth, then," the younger boy says, voice small. "That's what happened to her."

"Yeah." It's all Dean is able to manage. He feels numb. All these years of wanting answers, yet now they have them, it seems to explain nothing. There's was no reason for Mary to die. No reason for the company to cover it up, other than to hide their own dangerous obsession with the creature. Dean's fists clench. Mom, Dad, Anna, Cas, and so many others, all dead because the company values the xenomorph higher than human life.

"She died fighting that thing," Dean says, voice like steel. "So did dad. We're not gonna let it be for nothing."

"Dean?"

"There's more of those things still on board this station," he says, standing up. "And the company isn't going to get its hands on them. They can't be allowed to escape, or run the risk of someone else finding them. We're gonna blow them all to Hell."

There's a pause as Sam looks up at him, taken aback, and then a similar look of grim determination settles on his face. "Yeah. Let's get the fuckers."