The Doctor was frightened. In nine hundred years of time and space, he had never experienced the feeling of both hearts stopping, the air disappearing from his lungs, and the loss of movement all at once. He couldn't see: his eyes had closed as he fell, but he hit the ground hard because he could not break his fall. He heard Donna call out to him, but he could not respond. He heard and felt her footsteps, running towards him, back and forth across the soil and grass. I'm here, he wanted to shout. I'm right here, Donna. But then she found him, her footsteps stopped, and she was shaking him as if trying to wake him up.
"Doctor, please, please, get up!" his companion said desperately. "I can't do this on my own! Please say you're still alive, please!" He had never heard her quite this desperate before, except perhaps on the Oodsphere, when he had let her listen to the Oodsong and she couldn't stand it. She pressed her hands against both sides of his chest, feeling for a heartbeat from either heart. She couldn't find one. "How do I…?" she said quietly. Then she did what she had seen the Doctor do many times before: she placed her hands on either side of his head and pressed their foreheads together. "Oh, let this work," she said.
The Doctor really was proud now. See, this was why he had chosen her. She was so clever. Although he wasn't sure it would work, he sent her the telepathic message she wanted. Oh, well done, Donna Noble. She gave a tiny squeal. "Did I do it? Did I really, really do it?" she said out loud.
Yes, of course. It was so difficult to send these messages into humans' funny little brains. The messages had to be so oversimplified. Now, listen, Donna, if I heard you correctly, you found the little boy Deyno told us about? Don't try and answer that, actually, I heard you. Take him back to the TARDIS. Leave me here. Take him back to the TARDIS. Tell him we're going to figure this out, and leave him next to Yenna. Tell her that her husband is back and her daughter is fine. Do not come back for me. Stay in the TARDIS.
"But what about you?" Donna asked nervously.
Oh, you know me, I'll figure something out. What he didn't tell her was that he had caught a glimpse of the creature (for creature it was) that had caused this mess, and thought he knew how to fix everything. But he needed her gone first. He needed every tiny molecule of his brain focused on one task. Because the creature, whatever it was, had linked itself to the Doctor's mind. And if he could find the link, he could reverse the process.
Surprisingly, Donna obeyed, although reluctantly. She pulled away from the Doctor and let him lay back down onto the ground carefully. It must have been hard for her, but she left. As soon as she was gone, the Doctor began to search in his mind. There was some sort of link, he could feel it, that was draining his body's ability to function, like a sort of energy transfer, with the other end linked to the creature. He could also tell that the creature communicated telepathically. It was very advanced, so much more than the humans, although not as advanced as the Time Lords. Still, it was very impressive. All right, he thought to himself. Allons-y.
With an incredible amount of focus, the Doctor felt his consciousness fade away from everything in his surroundings, trying to find the physical location of the link. It took a long time, and an exhausting effort, but he let every memory he had sink into nothingness. When everything but the task at hand was suppressed, the Doctor found that it was fairly easy to find the link.
And then sever it. With a jerk and a gasp, the Doctor felt his hearts start beating again and his entire awareness flood back to him. Coughing and spluttering, he rolled over and forced himself into a sitting position. His eyes snapped open and blinked against the fierce light of the alien sun, reflected off the shining gold and green grass. And I don't think, he reflected, standing up shakily, that I've ever seen anything quite this beautiful.