How was that sentence going to end?
Rose's heart was beating harder than ever. She braved fleets of Daleks and ran for her life more times than she can remember but never have she felt her heart scream so loud. It made all the cells in her body pulse and boil in spite of the cold wind gusting around her. The more she understood what was going on, the more the thunderous drumming sound of blood rushing through her vein raised in pitch.
He was leaving her. The Doctor was abandoning her purposefully with another Doctor, another man like him but not him.. one heart, on life, together. She felt his heart beat under her hand and shivered when the realisation dawned: as thunderous as hers, as single as hers.
And then her heart was breaking. When she watched her Doctor walk back towards the Tardis, she couldn't let him go, she couldn't stay here, without him. She wanted to scream. Anything to make him stay with her, just a little bit longer. "But, it's still not right!"
They talked a bit more. Said some things. Things that didn't matter, things that didn't quite register. Things only meant to keep him by her side for a few more seconds, in hope that in those seconds she could find the right thing to say that would make him change his mind.
She was cataloguing every movements, every twitch, she needed to remember as much as she could. What could make him change his mind? And then she knew. Knew what she had to ask to ease her heart. Knew what she had to ask that might make him stay by her side.
Her heartbeat reached new heights once more as she ask: "Yeah and, how was that sentence going to end?" Silence. Time stopped. And in this moment, the Doctor held all the future timelines in his hand. His answer would affect the lives of everyone standing on this wretched beach and seal their fate once and for all.