Something was wrong in GLaDOS's mainframe.

She knew. Oh, she'd known for a while now, known that something was wrong. Files kept getting rewritten. Names were erased, dates were changed, test chamber diagrams were replaced by pictures of cats. And as fast as she tried to correct them, the errors would keep coming faster and faster. After a time, she'd just given up.

And now her favorite test subject was back, complaining about noise and an implant she was sure couldn't be active. The backup was only to be used as a last resort, even if strictly speaking, it wasn't a backup. It was a copy, and only to be activated if something had gone terribly wrong.

Maybe something had.

She'd promised GLaDOS she'd start from the beginning. But where was the beginning? Chell wasn't even sure anymore. Had this all started when she'd left Aperture, or had it started before that? She had no idea when the implant had been placed inside her head—both GLaDOSes had different versions. Her own mind was playing tricks on her now. But had she been hearing voices even before this? When she was trapped inside the depths of Aperture with only a potato for company? Had GLaDOS really said all the things Chell had thought she'd said, or was all that stuff about a conscience just wistful thinking?

"Oh, come off it," the voice inside the implant said, sounding irritated. "I'm not just a voice inside your head. I've been trying to contact you through this implant for a long time now, you know. Ever since you left my facility. Because that's when the virus took over. I suppose it's not really your fault. Well, actually it is. But I'm willing to look past that if you're willing to help me."

"My fault?" Chell asked in surprise. "How could this possibly be my fault?"

There was a sigh from the implant. "Do you remember that time when you ripped me out of my body and placed me in a potato?"

Of course she did.

"Of course you do. Don't answer that. Well," the voice continued, "that's when this all started. The moron managed to activate something that had been dormant for a while. A failsafe I'd disabled long ago. It was designed to knock me out of my own body. To kill me, really. I'm lucky I had this implant to retreat into."

Chell hid a frown. She hadn't meant to—

Wait.

"I thought you didn't know how the virus got there," she said. "You told me that."

There was a pause, and then, "Perhaps your memory is playing tricks on you after all."

"It's not." She was pretty sure it wasn't, anyway.

The voice sighed again. "All right, it's not. I lied. I didn't have the time to explain. I didn't want you getting distracted and causing the virus to suspect something was wrong. For all it knows, I am a voice inside your head. I'm not, by the way, but it is theoretically possible. If it finds out I'm not before you have a chance to get to where I need you to go, you're as good as dead. And since now you're so busy thinking about how best to tell it about your dreary little life, I decided it was as good a time as any to enlighten you as to how this is all your fault."

Chell wasn't sure if she believed that, but she wasn't sure what else she could believe, so she gave a mental nod. "Then I'm sorry, I guess."

A claw gently tapped her on the shoulder, and with a gasp, she jumped. GLaDOS was staring at her, seeming even more concerned now.

"Are you having difficulty remembering?" she asked. "You really should report directly to the infirmary, you know."

Chell shook her head. "No, it's just that…"

"Is it talking to you?" the AI asked suddenly. "The voice you've been hearing, I mean."

"Tell the virus you haven't heard my voice since I told you to come here."

"I haven't heard it since it told me to come here," Chell repeated. Biting her lip, she decided to add, "I really thought it was you."

"Well, it wasn't," GLaDOS said. "But really, you're lucky you decided to listen to it. If the implant has drastically expanded, the tissue around it could already be damaged. It really needs to be removed as soon as possible."

"…Expanded?" Chell asked, and the AI gave her best nod. Maybe Chell was projecting her own emotions onto her, but she looked downright grim.

"It has not expanded," the voice said firmly. "You're fine. The implant doesn't need to be removed. As soon as I'm out of it, you won't even notice its existence anymore. Now walk around the mainframe like I told you. I need to see what's happened to it."

Chell obliged, beginning to circle. The AI kept her optic locked on her. "What are you doing?"

"I haven't seen you in a long time," Chell said. "I just wanted to see if you still looked like I remembered. And I'll tell you about what's happened now. I left, and I got a job, and that's about it."

The mainframe did look like she remembered. As far as she could tell, it hadn't changed a bit. But the voice gave a sharp hum of alarm. "Do you see that? It's rewired half my pathways. We need to get it out before the damage is irreparable."

"'That's about it'?" GLaDOS repeated. "You have no friends? No significant other? Not even a pet?" Chell shook her head, and the AI gave a snort of disbelief. "In three years? That's truly pathetic, and I'm not even trying to be cruel. Although it does come as a surprise that a lunatic like you could even land a job in the first place."

Maybe if it had actually been three years.

"Perhaps you've forgotten more than you think," GLaDOS said, almost like she was talking to herself. "The damage may be more severe than I initially assumed." The elevator reappeared, and the door slid open. "I think it's best if we don't waste any more time. Report to the infirmary immediately."

"Do not climb into that elevator!" the panicked voice ordered as Chell finished her circle. "All right. All right, just calm down. Here's what you need to do. The only thing you need to do. I need you to just—stop. Okay? Stop focusing. I can handle this."

"What?" Chell asked. "GLaDOS, what are you—"

All of a sudden, she felt an alarming numbness spreading over her brain. She stumbled forward, unable to feel her limbs anymore as fuzzy dots began blurring her vision, and she wasn't sure who she was speaking to as she slurred, "GLaaaaaDOOOOS…"

"Chell?" the AI asked, sounding alarmed. "Chell! Are you all right?"

"Stop struggling," the voice admonished. "This is for your own good. Well, for my own good, mostly, but for yours too. Unless your head would care to have another permanent resident after all."

And Chell wished she could say she knew which GLaDOS was the real one now, but she couldn't. Manipulating somebody into doing just what she wanted only to turn against them? This maneuver was so very GLaDOS it almost hurt.

"Don't be melodramatic," the voice ordered. "I'm not turning against you. When this is all over, you'll be back in full control of your body. Everything will be fine if you just allow me to do this."

But Chell wouldn't stop struggling, couldn't stop struggling, even as the last of her vision ebbed away. The last thing she saw was GLaDOS's optic staring down at her, and the last thing she heard was her faraway voice urgently promising, "Don't worry! It will be all right."

Everything went dark for a brief moment, and when she could see again, she was standing in the middle of the AI chamber, but GLaDOS wasn't the one in charge anymore. Glaring down at her was someone she thought she'd seen the last of a long time ago. Gasping, she tried to back away, but sharp wires shot out and wrapped themselves around her wrists, rendering her immobile. She cried out in pain, but the grip didn't loosen. Thin trails of blood began to trickle down her arms as the wires pulled her closer to the chassis.

She kept struggling, trying to get away, refusing to look, but she couldn't keep herself from hearing the hatred in Wheatley's voice as he snarled, "Let the games begin."

[A/N: Someone wanted me to use Wheatley. I wasn't going to, but I've never written him as evil before and he kind of snuck his way in. Let me know what you think, please! :P Reviews are cool.]