She wakes one night to the sound of her own screams, still half-lingering in her nightmare.
The Doctor appears in the doorway, silhouetted by the hallway light, and he makes it to her bed in two large strides. He folds her shaking body up in his arms, pushes her damp hair back off her sweaty forehead and rocks her gently back and forth. "Ariel! Ariel, it's okay, it's alright, it was just a dream, I'm here. I'm here."
"He was drowning," she whispers, hand curled tightly around his shirt.
He doesn't stop rocking her. "Who was drowning?"
"The human. He was so beautiful..." Her breath catches in her throat. She squeezes her eyes shut, breathes in the Doctor's familiar scent. "He was on a ship, and there were these lights in the sky, such pretty lights, all different colours. But then it started to storm, and there was fire, everywhere, so much that the water couldn't put it out and suddenly the ship was gone and he was alone in the water. He went under and I tried to save him, I wanted to save him, but I couldn't move, I couldn't swim to him... He drowned..."
He murmurs into the crown of her head. "It was just a nightmare."
"I feel like I know him, though. Or like I should know him. But I don't, I've never even seen him before."
He stops rocking her. She pulls back to see his expression. His brow is creased, but when he catches her looking he smooths his features. He gently lays her back down in bed and stands, scratching his cheek absentmindedly. "Try to get some sleep. I'm right outside if you need me."
She can't think of anything else to do, so she just lays down and watches him retreat from the room.
"Doctor," she calls when he has his hand on the door handle. "Leave it open, please?"
He smiles at her. "Of course."
She listens to him walk away, and tries to forget the sound of the waves that threaten to drown out everything else.