The thing inside Amy made her hand go up, grab the barrel of the gun, and pull it to her forehead. River's eyes grew wide- Amy's face didn't change.

"This gun has much force. When you pull the trigger, the speed and resulting explosion the bullet causes going through the skull will create a cloud of blood. We believe it's called the 'red mist'. And millions of us will be in the red mist, and we will spread, fill the air of this place, invading every living creature inside this place. And your mother will be dead," H-S1 said robotically, the underlying buzz grating on River's ears.

Her hands trembled.

MNMNMNMNMN

The Doctor produced three clip-on-ear walkie talkies from his pocket. "Borrowed from Torchwood." (Hundreds of years and thousands of light-years away, Jack discovered the missing mics and swore.) "Work very long distance- keep the radio on at all times so we can stay in contact. Ood-Sigma… you can clip yours to your, erm, face tentacles," he said quickly. Rory took his and hesitated.

"You're talking as if we're in danger, not Amy." The Doctor didn't reply, and Rory let out a weak laugh. "I mean, she's sick. What could she do to us?"

"I don't know, Rory. Honestly, I don't. I just want to be prepared for anything." He clipped on his mic. "I'll ask the TARDIS to rearrange a bit so we can find her quickly, and to lock the doors to any dangerous rooms, but there's no guarantee she'll listen. She's still a bit in shock from TL-S13, and cleaning up the blood in the control room." Rory noticed he avoided saying that it was his blood. "She's all befuddled. I've locked the console controls to everyone but me, so Amy can't mess with anything, but I'm not sure she's up to anything else, poor old girl."

"You think Amy will try to fly the TARDIS?" Ood-Sigma questioned.

"It's not Amy. It's H-S1," Rory corrected angrily.

"Apologies," Ood-Sigma bowed, while the Doctor rubbed his forehead.

"I don't know, I don't know! I'm just… preparing for anything. Prepare for the worst, hope for the best. We don't know what this thing wants. That's what we need to find out first- maybe we can get it to leave Amy. We don't even know if it has any malignant intent. It's mutated, and new to being cognitive, and I'm sure it's confused. Point is- we've got to find her. Rory, take that way, stay out of any dark corridors. Ood-Sigma, follow Rory until you meet a fork- one take one way, one take the other. I'll head this way. Coms open at all time. Be careful." He nodded to both of them, and they parted.

MNMNMNMN

"Why?" River asked, her voice cracking. The gun was still pressed against her mother's forehead, pointed at the parasite-virus she'd created.

"We don't understand. Clarify your question," it said.

"Why did you find me? I can't do anything you can't. The only way I could help you would be to fly the TARDIS, but obviously you can already handle that," River whispered. "So why me?"

The thing smiled with Amy's mouth. It wasn't actually even a smile- just pulling the face muscles so her mouth curved into a concave-up line. The rest of her face didn't change- just a smile on her lips.

"Tell. Me." River's eyes narrowed.

"The phrase that applies here is 'playing it by ear,' we think. You created us. We're sure you have other ways to help us, other than the cognition, full-body possession, and hosts you've given us already. Also, we are following a rule of human life that we believe is called 'rubbing it in,' something akin to rubbing dirt in a wound, except the metaphorical dirt being words or meaning, and the wound being only a mental or emotional wound."

As Amy's mouth spoke, River's shoulders sagged, more and more with every word. Her eyes dimmed, and gun lowered, until she was staring at the floor, gun hanging uselessly from numb fingers. A deep, shuddering breath rattled her shoulders.

The virus put its lips beside the defeated River's ear. "Take us to the control room."

MNMNMN

The Doctor dashed down a hall, knocking open every door he came across, peering inside for half a second, then continuing his mad rush.

"C'mon, think think think," he muttered, throwing yet another door open, glancing at the aquarium inside, and bouncing across the hall to open another one. "Where would it go? A newly created virus, cognitive… but how cognitive? Does it have wants and dreams and aspirations? Or does it just understand what's vital to it? What do possessing parasite-viruses want?"

He rushed around a corner, sliding slightly on the smooth floor, checking more rooms. "It's a virus in a time-space travelling machine. Does Amy have any influence over it? Did it push her out of the way, or did it engulf her? If Amy was still in there… the virus would've infected Rory, not taken off. So it's thinking like a virus, not like an Amy-virus hybrid. Right."

"Doctor, we can hear you," Rory's irritated, slightly out of breath voice said in the Doctor's ear.

"Yes, yes, mouth thinking, shush," the Doctor exclaimed as if it was obvious. "So… what does a virus want?"

"Hosts. Bodies to infect, and lots of them," Rory replied.

"I wasn't asking you! Just thinking! So, what does a virus want? Oh! It would want… hosts. Lots of hosts, bodies to infect," the Doctor realized, hitting himself in the forehead.

"Rory just said that very thing," Ood-Sigma pointed out.

"Shush, you. So it wants lots of bodies. It wants… Earth. They always want Earth," he grumbled, slamming a door extra hard. "Earth… so it tries to get to Earth. But it doesn't know the TARDIS, does it?"

"There were trace strands of your DNA in the nucleus of the H-S1 virus we observed, and you said a single cell of a Time Lord-," Ood-Sigma said.

"Oh, right! So it does know the TARDIS! Actually," he interrupted, then stopped, freezing. His face paled. "It has my DNA. Inside it. Part of me… Rory! Ood-Sigma! Head for the control room, now! The virus, it has a link into the TARDIS, as strong as mine, maybe stronger. There are millions of the virus inside Amy, with hundreds of strands of my DNA. It could move corridors, rearrange rooms, do whatever… It will think it can fly, but I locked it out, so it'll head for the control room." He turned around and began sprinting down a side corridor, tweed jacket flapping behind him.