Part 1: Contact
"When you look into the abyss, the abyss looks back"
Looking back, I'm not sure what I thought was going to happen when that crazy bitch showed 784 the photo. If I had to put money on it, it would have been even money between screaming at her for lying and going completely apeshit and killing us all.
No one, I think, would have dared put down money on saying, "yesssssssssssssssss. i know."
Valentine, that crazy bitch, didn't even bat an eye. "I thought you might. How did you guess?" she asked.
"bbbb-b-beatrixxx madadadadadox is asset to foundationn. Foundation would ud not lettitititttt her die without without a f-fi-f-f-fight," the monster growled.
She looked sternly into the cold blue eyes of the roiling mass of silicon and steel. Her lips, I noticed, were pursed slightly tighter than normal. 784's tells were harder to see, but after months of watching that thing, I could see the rhythmic opening and closing of its spiracles accelerate, just a bit. "Yes, of course," Valentine said. "Just like we're not willing to let an asset like you just sit around inside this box." She leaned against the railing, reached for a cigarette, realized that she was wearing a hazard suit, and settled for crossing her arms. "Beatrix Maddox's body was recovered from the incident site and regenerated," Valentine explained. "However, the process was… incomplete. I believe the technical term is, 'locked-in syndrome.' Her brain and body function just fine, but they don't talk to each other. She is completely awake, but unable to control her body."
784 didn't respond to that. Its blue eyes nicitated once. "The Foundation has determined that the only method remaining to us is a dosage of Five Hundred," Valentine explained. "As SCP-500 is a finite asset, we are… shall we say… let me just say there is opposition to the idea of using it on a simple agent. Especially one who is officially dead."
"B-bbbbargaining ch-kkchckip."
"You see it already, then." Valentine chuckled. "I have been authorized to form a new Mobile Task Force, designation Delta-Niner: Feynman's Folly. Twelve member team, assigned to support you in the field. You will carry out missions containing and capturing particularly difficult SCPs. As a former member of Pandora's Box, that should be familiar to you. In return, Agent Maddox will be given a dose of SCP-500 and restored to her prior state. Is that sufficient?"
"W-w-wwwwill I bebbbbbe able to s-sssse her?" 784 asked.
"Of course not. Don't be ridiculous," Valentine scoffed. "She will be given a Class A Amnestic and false memories will be implanted under a new identity. On the other hand, she'll be alive, and happy. And in the end, isn't that all you want? For her to be happy?"

When I was a kid, I was riding in the front seat of the car when a pickup truck cut into our lane in front of us in the middle of a heavy rainstorm. My mom hit the brakes, but the car hydroplaned out and slammed into the truck before spinning out into the shoulder.
Even now, the thing I most remember isn't the moment of impact, but that moment when the car started to skid: the sick feeling of realizing that we were going to crash and nothing I could do could stop it.
"HIT IT! HIT IT NOW!" I screamed. The Deltas glanced at each other, hesitated just for one moment. It was all that 784 needed.
"no."
Just one word, spoken with crystal clarity in the midst of its inhuman, buzzing voice… then the three D's fell dead with nanomachine spikes through their foreheads. Valentine screamed, and then the tendrils lunged forward and wrapped around her, dragging her up into the air. A thousand cruel, sickle-like blades formed themselves around her in an iron maiden, barely dragging against the surface of her hazard suit. "SECURITY!" I screamed. "EMERGENCY SPRAYERS, FULL…"
"WAIT! WAIT! WAIT!" Valentine screamed. "STAND DOWN!" She turned back to the cold, implacable eyes of 784's optics, unafraid of the razor-edged blades. "wait…" she repeated.
"fleshhhhh esh flesh matitititititttters flesh matters not," 784 chitters. "only only mimmmmind."
"I can't let you see her," Valentine said, "but I can cancel the order for the Class A Amnestic. Would that be sufficient?"
"sufficient," 784 whispered. The blades retracted, and the nanomachine tendrils lowered the Director to the ground.
"We'll be in contact with you regarding your first mission," Valentine said.
"wwuwuwuuwun reskkkkkkkkkquest," hissed 784. "nnnononono acetetetetetatone bath. not neinnnnneeded."
"Agreed. Mister Lorenzo, you will keep 784's containment chamber outside the acetone pool as long as it continues to cooperate with us," Valentine ordered.
"Ma'am, with all due respect, that's completely fucking loco," I hissed. "That acetone pool's the only thing stopping it from growing out of control!"
"Not any more. Now it wants to cooperate. Don't you, Andrews?" Valentine asked.
"will cooppippppperate," 784 hissed. "kikkkkeep your endiddddd ofphh the bargain." The tendrils retracted back into the concrete holding container, like an anemone retracting back into its polyp.
"Security, unlock the main doors. Let's go, Lorenzo."

The solvent bath washed over our plastic biohazard suits, cleansing any traces of nanomachines remaining on our bodies. Valentine spent the entire five minute cycle leaning against the wall, arms outstretched, her head thrown back and staring up at the ceiling. It was honestly kind of spooky.
"It's beautiful, isn't it?" Valentine said, as we were changing out of our hazmat suits.
"Excuse me?" I paused in the middle of shrugging into my labcoat.
"That body of his… gorgeous." Valentine touched her throat as she adjusted her collar, then ran a hand over her steel-grey hair, which was starting to come loose from its severe bun. "It'll never grow old, never decay. Limited only by his willpower and mind… and such a mind it is. Can you imagine what he could accomplish, if he could only master it?"
"Ma'am," I said, slowly. "Are you feeling all right?"
"Yes. Better than all right, I think." Valentine said. She pulled on her labcoat. "I'll submit a report to Director Clef. The first mission assignment should come in this week. Make sure he's ready for it."
"As you wish, ma'am." I waited for her to leave, then headed for the control center as fast as I could. "Herrera?" I said to my assistant. "I want double-shifts around the clock. At least two pairs of eyes on this thing all the time, and one guy with his hand on the sprayer controls: I want this thing watched closer than 173. And put in a request for some replacement Deltas, and have the old ones removed before I get back."
"Sure thing, boss. Where are you headed?"
"I'm gonna talk to Smiley," I said. "If I'm not back in an hour, tell the medics that there's a dead man with a shotgun wound in Clef's office."
Part 3: Escalation