"So, this plan." The Doctor bounced a bit on his toes. "Let's hear it."
"River had a dig on a planet where there had been a small society of people with technology that could separate or combine different minds within the same brain. They believed that the body is just a tool or transport. Something naff you wear 'round the house on a Thursday evening. It's not who you are, cos all you really are is your thoughts. So they swapped consciousnesses as a religious rite or somethin'. Used it for loads of things, like as a getting-to-know-you, or learning compassion by walking a mile in someone else's shoes. Apparently it was like a physical form of telepathy for those of us without the natural ability." Donna sniffed. "Poor sods, imagine what their marriages were like. Is that what it was like for Time Lords? Come home one day and your husband is some other man? Or a woman. Did that happen? Cor, that would keep things interesting."
"Donna!" His offended countenance was less effective when he was trying to clamp down a giggle.
"Sorry," she said, completely unapologetically. "The team found traces of a lost temple where this would have happened. That wasn't the focus of their expedition, so they left it uncovered for later. We should be able to get what we need from those ruins. Or from the people if we, y'know, go visit them before they died out. Need a scanner thingummy and holding vessel. It's an organic brain analogue, River said. Then her template can be programmed into a Flesh avatar without an original body cos the vessel will read as alive. You'll have to sort that part."
"My ship is at your command. Where are we going first?"
Donna punched a few buttons on the vortex manipulator, then held up her wrist up so he could read the coordinates on the small, green display. The Doctor blinked, the tiniest of expressions, but the redhead noticed. He then immediately favored her with an affable smile.
"That is... Falxia Meridiem, 7th century of the Cantalvion dynasty! Easy peasy." He laughed in his staccato way and stepped over to the console.
Donna lounged against the platform railing, enjoying the first peaceful moment since she had arrived. She watched the Doctor at work. Flipping a toggle switch with an elbow, plugging his sonic screwdriver into the dashboard with a flourish, then twirling around to dial in a complicated pattern of buttons. He was clearly pleased to have an audience, as Donna knew he was flying the Tardis in a manner more flamboyant than necessary. When so many of the details had changed, seeing the Doctor in his element was soothing in its familiarity.
Something itched at the edge of her perception, like the whine of a mosquito near her ear. Donna tossed her head in irritation but tried to ignore it. A new Tardis interior could mean new sounds. It was getting louder, now an audible droning hum that set her teeth on edge. It modulated in pitch, never staying the same for more than a second. She looked around but couldn't pinpoint the source. The buzzing was equally loud from all directions.
"Is this weirdo alien music? Are you into dubstep now? Cos I don't fancy a concert from DJ Bleedin' Bowtie at the moment! Only dogs could hear the whole thing properly," Donna complained over the din.
The Doctor paused and looked up from where he was bent over the typewriter. Craning his neck, he peered around the room. He gave her a cheery thumbs-up and went back to work.
The mechanical whalesong of the Tardis in flight was overpowered by discordant screeches. Donna thought the usual vworp vworp landing noise would be like angels singing next to this racket. She could feel it in the soft tissues of her throat and gut; even the railing behind her was vibrating under the force of the sound. She stuck her fingers in her ears and bellowed, "DOCTOR!"
"Wait, don't cover your ears," she saw the Time Lord mouth as he bounded over. He stuck his hands out in front of him, palm up, in invitation. She reluctantly took her hands away from her ears and winced as sound seemed to flow directly down her brainstem. "I'll turn it down." He aimed the sonic over his shoulder and the noise reduced to a tolerable level. It was now just one constant tone.
"What was that?"
"Just had to triangulate your position and find the right frequency." The Doctor pointed with false modesty at one of the round metallic things embedded in the coppery Tardis wall to her right, then another one on her left side. "Speakers, among other things."
"You did that on purpose!" Donna swatted at him halfheartedly. "Thanks for the warning."
"Sorry, couldn't tell you before, cos it had to be unexpected. We've got some privacy now. Sound's blocking any little eavesdroppers on board," he said as if the prospect of spies were rather thrilling.
"There's only just us here." Despite knowing this, Donna glanced down the hallways that lead further into the heart of the Tardis.
"Wasn't counting noses, Noble." He drew a little circle on her forehead with his fingertip, then tapped the center of it.
"River? What do you have to hide from her?"
"Nothing. Everything. Just need some time." He frowned, picking at some imaginary lint on his sleeve. "It's... complicated," he amended finally.
Donna rolled her eyes. "If you're gonna be like that, I'll just go sleep off the headache you gave me with that stupid noise." She started turning to leave, but the Doctor blocked her path. The concerned look on his face stopped her short more than his physical presence.
"Don't go! It's important that you stay still, exactly here. Just for a few minutes so we can talk."
"Why? What's so special about this spot?" She raised an eyebrow at him but returned to her original position.
"It's not, it just happened to be where you were standing when I calibrated the signal. The speakers on either side of you are aimed directly at the corresponding ear, creating a localised auditory field. Like headphones. Each side is playing a separate frequency, but the human brain blends them together into a single wavelength, so it sounds like you're only hearing one tone. They call it binaural beats in your time. The neural oscillation I set up here is canceling out the gamma brain waves linking your conscious mind to the subconscious. River is alright, but she'll be deaf and blind... and probably very very cross."
"There's a safe bet, sunshine. Assumin' you have a reason for the cloak 'n dagger, how d'you know it worked? I don't feel any different except for the buzzing eardrums."
"Mm. Going to try something. Quick test. Let me know if you feel her react. Though I'll probably be able to tell because of the violence." He unfolded some red fabric from his pocket. Moving with deliberate care, the Doctor placed a fez on Donna's head. "Anything?"
Donna struck an exaggerated fashion model pose. "Does this mean you're finally takin' me to the Planet of the Hats?"
The Doctor's eyes lit up. "I could get one of those fuzzy ear flap hats. A ushanka. Those are cool," he said longingly. "Nah. Stuff to do first. There's always stuff. I'm fairly sure that River is cut off or she'd have something to say by now. May I have the manipulator?"
Donna removed the wrist strap and handed it to him. Bleeping it first with his sonic, the Doctor squirreled the cuff away under the console in a drawer that wasn't there a minute ago. He retrieved something from the hidden cache and slipped it in his jacket pocket. When he turned he saw Donna watching. "Preparing for the fallout. As much as I wish... You were right. I can't control what's happening here. But maybe I can guide it a bit, minimise the damage." He glanced at his gold wristwatch and frowned. "Breakfast time in England. No one likes tears before they've had a nibble in the morning."
She slumped back against the metal bar. "You sound like you still think this is gonna fail. Like I'm just doomed. I spent six months working for this chance and it's not even worth trying."
"No no, it's not like that. I promise. I'll do anything to save you, no matter what. Trust me?" The Doctor pulled Donna into a hug, where he felt her nod her agreement against his shoulder. "The thing is, your plan's rubbish."
"What?" She pulled away from him.
"River was adamant that I not get a peek inside your head." The Doctor dropped into a stage whisper. "Why do you suppose that is?"
"She- she said it could disturb the balance she had struck against the metacrisis energy." Donna could barely hear her own voice over the drone of the speakers and her own insecurities screaming in victory.
He laughed, a drawn-out haaaa. "The first thing you should know about River Song, or the first rule if you prefer, is that she lies. What she told you about a scheme to resolve the metacrisis with an artifact and get herself a new cloned body. It's a ruse. Wouldn't work; not even meant to work."
"How can you be so sure?"
"Her diary. I may have, um, read it. After Darillium there were no more spoilers, so I didn't see the harm. Other than her killing me when she finds out. The risk of that seemed really small at the time!" He gulped. "She documented her whole life in that book. Everything. She couldn't have been on an archeological expedition that turned up a convenient mystical consciousness-separating relic on Falxia Meridiem. River's never been there."
The redhead's face flushed with anger and betrayal. "This whole time she was just connin' me? Havin' a laugh at dim old Donna? I thought she was my friend. If I manage to get her out of my brain and into a solid body, I'm gonna kick her arse!"
"Oh, Donna. I didn't say your friendship was fake." The Doctor caught one of her clenched hands and awkwardly petted it. "Just the method of getting you here. River's always had her own ways of accomplishing a goal. Likes to take shortcuts through the grey areas. It's clear she cares for you a great deal." The tension in Donna's arm reduced somewhat.
"Before my memory was restored she could have told me that there was, I dunno, a clinic in Sweden that specialised in neural pathway reconstruction, and just popped over here instead. If all she wanted was to get me back on the Tardis, she could have dropped the act at that point. There's something else, just not what she told us."
"That part was for my benefit, I'm afraid. Wouldn't be surprised to find myself temporarily stranded on Falxia as soon as I walked out the doors. Put the Doctor where he can't interfere. Cos she knew I would. Or I would have, before you talked me out of it." He took a great breath that was almost a sigh. "Now she must know that I know. I know that she knows I know, and she knows that I kno- This is going to get repetitive. Let's switch the metaphor to seeing chess moves ahead. No, no. I hate chess. It's boring when there's no voltage. Are you at all familiar with the Royal Game of Ur?"
Donna was glaring at him. "A point. Are you ever able to arrive at one?" she asked in clipped tones.
The Doctor appeared to feel the burden of every one of his 1600 years, his head sunken to his chest. "I know what River's doing now. And I'm going to let her."
He approached the console again, flicking switches that brought the glass bauble of the time rotor to life. There was a slight jolt as the Tardis landed at her destination.
"Donna, I'm sorry. You can't share a body with two other consciousnesses, it's not stable. The metacrisis can't be removed. River can't be transferred out in the time you've got left. The only way that everyone survives is to wipe your memory, which you both refuse. When I said before that there wasn't a solution, I meant it. There's nothing I can do." The Doctor's brow furrowed. "But I think River found a way, if she lets the metacrisis go and channels the energy."
"You said I'd burn if that happened."
"And you would have done. The human mind wouldn't be able to cope. The metacrisis is a fragment of regeneration energy lodged in your head. You wouldn't know what to do with the power that's unlocked. It would try to rewrite you entirely, replacing your mind with the merged copy of mine. River's part Time Lord. Regeneration is instinctual for us. She could direct the power, use it up. You'd be fine." He smiled, but it didn't quite reach his eyes.
"That sounds like a good thing. I would like to live, y'know. But you look like someone stole your sonic and made you eat a pear. You're not tellin' me everything, Spaceman."
The Doctor dragged his fingers through his hair. For a moment he was silent, seeming to weigh his words. "River's consciousness will be consumed along with the metacrisis."
There was a knock on the exterior of the Tardis doors. "Hey, Doctor," a female voice called from outside. "Want to join us for breakfast? Rory's cooking omelets."
"But she doesn't have to do it alone. Old Girl, be a lamb and let the Ponds in, won't you?"
The Yale lock clicked itself open.
TBC
A/N: Sorry for another cliffhanger- this was supposed to be the last chapter, but it kind of got away from me. Thanks for your patience :)