you're brilliant
a/n: added a bit to the end of it, since the scene was so painfully short. I took a guess at which scene came after, so sorry if it's out of sync with the episode.
She felt like her heart had split in two and settled into the bottoms of her feet. It was the only way she could describe the sensation. The fear, the horrible dread that had overtaken her, weighed heavier and heavier as she crossed the room. She felt every step she took in her bones, could hear them echoing in the silent house.
The Doctor looked up from the rock he'd been inspecting as she approached. She got down on her knees next to him, folding her hands into her lap.
"Seventeen years old and her arm's turning to stone," she said quietly. The disbelief was clear in her voice, but she honestly didn't know what was more unbelievable to her. That of all places, of all times, they would have touched down on the day before Vesuvius erupted. That the girl's arm—her arm, her literal arm—was turning to stone. That—
"All the soothsayers of old Pompeii can see the future," the Doctor said, eyes on the ceiling as he processed this. "And yet none of them can see tomorrow."
She remembered the stand-off between the old man and Evelina and wondered, briefly, at the things they'd said about him—and her. You've something on your back.
"We're staying," she found herself saying, as if there had been another option. It didn't strike her until the words were out of her mouth that there was.
"Yeahhhh," the Doctor said, dragging the word out.
She looked down to meet his eyes and he looked up at her. She could see the emotions swirling in his eyes. The confusion and worry and the tiniest thread of excitement, wanting to see what the universe has cooked up for him this time. He smiled slightly, put the rock he'd been holding on the ground, and held out his hand to her. She took it, half expecting him to pull himself up. He just squeezed it.
"You're brilliant, you know," he said softly, eyes flicking between hers. Ever since she'd joined him again, he seemed to stare at her eyes more than anything. She wondered what he found so interesting. "I was a bit harsh before—with the Time Lord superiority business. You're really brilliant."
She snorted, although her cheeks went pink. "You're daft."
"No, really," he said. His face was screwed up in confusion at her dismissal. "You are."
"And you really are daft," she said. She squeezed his hand again and then got to her feet. "Well, then! Evelina and her mother have promised me some clothes to change into, as I've soaked these in sweat. I must look a right mess…"
The Doctor's face screwed up again and he opened his mouth, but then seemed to change his mind. "Alright, then. You get changed and then we'll see about what we can do here."
Donna gave him one last smile and left the room.
She didn't know it, but his eyes remained on the doorway long after she was out of sight.