The other Doctor leans to Rose and whispers in her ear. He knows the words although he cannot hear them and then he watches as she pulls the other Doctor down and kisses him passionately. For a moment he just stands there, the pain burning in his heart.
Then he turns away and basically runs into the Tardis. He has to go. Quick. Before he can do something incredibly stupid, like pulling the clone away from her and begging her to come with him instead. Or cry.
She is so affectionate. She won't let him go if he cries. But he must.
She will be happy when he does. Not now, perhaps, not in one year. Perhaps she will always miss him as he will always miss her. Deep in his heart he hopes that she will. But eventually she will be happy. Only that is important.
Behind him the door falls shut. Donna. He turns around and tries to smile at her but fails.
"Doctor, we have to go. The walls are closing."
He can't move and she is at the console, pushing buttons, moving levers. Soon they have left the earth, left this world and are floating in the vortex. No going back. Ever.
He cries.