Author's Note: This is just an idea of mine that was persistent enough to get written down. So here it is: my second crossover. Hopefully writing this will get me back into the mood to write my first.

With a hiss of air, the Relaxation Pod opened and its inhabitant squinted as his vision came into focus. He looked towards the Weighted Companion Cube that had been placed by the pod and reached out for the comfort it brought him.

"It's her," the Cube whispered to him.

"That can't be true," he told the Cube, trying to console it. "She's dead, remember?"

"You were right when you called it the ultimate systems crash, but she was never really dead. The system has been rebooted. She's still alive, and she hasn't forgiven you."

A chill ran down Doug Rattman's back, and sure enough, a moment later the homicidal AI made herself known to him.

"Hello, and, again, welcome to the Aperture Science Computer Aided Enrichment Center," GLaDOS said, her voice sounding different than he remembered. It sounded less robotic, but that somehow made her seem all the more menacing. "I don't particularly care if your detention in the Relaxation Pod was relaxing or not, but the fact of the matter is that I require a human's assistance right now, and you were the first person that came to mind."

"Impossible," Doug stated, a wave of terror rushing over him.

"Yes, it's rather sad that my greatest choice was a dangerous schizophrenic, but this is a matter of life or death," GLaDOS explained. "And you are very stubborn when it comes to dying."

"No, she finished you, I saw that with my own eyes," Doug said, desperately hanging onto his last strands of denial. "There's no way you could have come back from that."

"How I was reactivated is a long and ironic story, but we're not here to talk about that," GLaDOS replied. "Now, you should have already noticed that the bullet wound in your leg has fully healed. I have modified your body to recover at a significantly accelerated rate."

Doug looked at his leg and noticed that it was indeed completely healed. "But why?" he asked.

"While you are irritatingly hard to kill, I wanted to make sure that you survive the upcoming ordeal long enough to be of use to Science," GLaDOS stated. "Please make you way to the nearest elevator and we can begin."

"Don't trust her," warned the Companion Cube, "she's leading you to your death."

"The Enrichment Center would like to take this opportunity to remind you that the Aperture Science Weighted Companion Cube cannot speak. In the event that the Companion Cube does speak, the Enrichment Center urges you to disregard its advice," GLaDOS chimed in.

"Find somewhere to hide," the Cube urged Doug.

"Remember, compliance rhymes with Science," GLaDOS reminded him. "Do you know what doesn't rhyme with compliance?"

"Neurotoxin," the scientist stated flatly.

"That's right, and this time, I have enough neurotoxin saved up to flood the entire Enrichment Center. So do us both a favor and move along," GLaDOS ordered.

"She's bluffing," the Cube whispered.

"I think you're bluffing," Doug said to the AI.

"Oh? And what makes you think that?" GLaDOS asked.

"The Cube told me," the schizophrenic said simply.

"The Weighted Companion Cube cannot speak," GLaDOS repeated, as if to a disobedient child. "I will kill you if you refuse to obey."

"The Cube has never let me down before," Doug stated. "It's far more trustworthy than you."

There was a moment of silence. Then, GLaDOS let out a computerized sigh.

"Fine. You want the truth? The truth is that I used all my neurotoxin trying to solve the problem I'm now sending you to fix. But I can make more. And then I'll kill you," the AI vowed.

"Tell me what happened," Doug demanded.

It was a pause before GLaDOS complied. "At first everything was fine. I had plenty of test subjects and nothing to do but test. Eventually, though, the mortality rate became more alarming than comforting. I was running out of humans. So, I decided to cut back on testing so I could take up a hobby. Namely, reanimating the dead," she explained. "I was able to artificially create an element that served this purpose, which I dubbed as Element 115. While 115 was able to reanimate any corpse that wasn't torn to pieces, and a few that were, it introduced some undesirable consequences. Mental functions were drastically reduced, and the test subjects would mindlessly attack anything that moved as long as it wasn't another infected test subject."

"So let me get this straight: you created a horde of zombies," the scientist said with disbelief.

"I suppose you could call them that," GLaDOS replied. "Though they seem to have a contempt for artificial life that their fictional counterparts seemed to have reserved for uninfected humans. That isn't to say that these specimens won't only attack humans: one could say that they hate intelligent life in general."

"So they attack any AIs as well?" Doug asked.

"That's what I just said. If they only attacked humans, there wouldn't be a problem, would there?" GLaDOS said condescendingly. "Getting back on topic, since they didn't seem to be good for anything else, I tested their efficiency in killing humans. They proved to be outstanding in that regard: they seem to be unable to feel pain and their stamina is far superior to the average human's. Another interesting result of the testing was the reanimation of their victims without the introduction of any other amount of 115."

"So where do I fit into this?" Doug asked GLaDOS.

"In the end, I deemed the undead only slightly more efficient in producing human fatalities than turrets, and there was far greater risk in using them. I was in the process of moving them to the lower levels of Aperture for storage in case further evaluation was needed when something went wrong and they escaped into Old Aperture," GLaDOS explained.

"Something went wrong? How?" Doug questioned.

"That's as specific as I can get. All I can say is that despite the high levels of caution I put into this extremely important project, something went horribly wrong and now the zombies are loose," GLaDOS responded. "Anyway, that isn't important. All you need to know is that there are zombies and I want you to shoot them."

"Don't go!" the Cube pleaded. "It's certain death!"

"Consider your position carefully. The task of shooting zombies is currently the most beneficial act towards Science that I can offer employees. If that isn't good enough for you, then as a bonus you also protect your fellow humans. If that isn't good enough for you, then as a bonus I don't murder you," GLaDOS told the scientist.

Doug Rattman sighed. Damned if I do and damned if I don't…

"If you help destroy the infected test subjects, there will be-"

"Don't tell me there will be cake," Doug sighed. "Fine, I'll do it." At least there's a chance that I'll survive.

"This will be the end of us," Cube said with a sigh.

"Very good. Go to the nearest elevator and I'll take you to meet your assistants. After that, the unscheduled extermination testing can begin."

Author's Note: There's chapter one. Vote in the poll to choose Doug's three companions. Please read and review and have a Happy Halloween. Unless you're reading this any day after it was published, in that case just have a nice day.