"Don't say that," whispers Donna. "Please don't say that, Doctor."
The arm around his back tightens, pulling him closer, and he swallows around the lump in his throat. He can feel the tension in her body, he notices the way her fingers, stroking through the shorter hairs at his temple, move a little rougher whenever he speaks.
"It's true though, isn't it?" he says, trying for a laugh, but his voice catches halfway through and ruins it. He clears his throat. "Donna it– it doesn't matter. You can let me go. It's fine."
Truth be told, there are very few places he'd rather be than curled up to her side, head on her shoulder, but he knows he's overstayed his welcome. He's only upsetting her—there's that tension again, like she's flinching from his words—and he's not worth her concern, and he doubts he can convince her anyway. He should leave. He should let her get on with her life on Earth, with people who won't hurt her.
"Stop it," she says. "Course it matters, I'm not going anywhere." She teases her fingers down to the back of his neck and resumes playing with his hair. He shivers, the persistent stinging in his eyes suddenly growing sharper.
"I know what you're doing, Spaceman." Her tone is gentle, not even slightly accusatory, but he wants her to stop. He only stays because he can't summon the energy to shrug off her arm. "I'm not gonna make you talk, I promise. You don't have to try to push me away."
"M'not," he mumbles automatically. "You just shouldn't have to–"
She silences him by pressing a kiss to his forehead. "I know you think you're all alone out there," she murmurs, "but you aren't. You prawn. I'm here to help, whatever you need."
Despite himself, he finds his nerves beginning to calm and the ache in his chest lessening. "'Kay," he whispers, glad she can't see his face, for the tears gathering in his eyes must be noticeable by now.
Giving his back a gentle pat, she says, "Get some rest, okay? I'll stay. Don't worry."
Without meeting her gaze, he nods, and lets her go long enough to lay down on the couch. He's back in her arms a moment later, a blanket draped over the both of them and his head tucked under her chin. He almost wishes he could bring himself to insist that she leave him alone, get some proper sleep herself and let him fend for himself. But, loath as he is to admit it, it's… quite nice. To feel cared for. And he doubts he can convince her anyway.
He falls asleep to the sound of her heartbeat and the feeling of her stroking his hair.