He's not the man the Doctor wanted. He's not the man he would have been. Amy weeps for him. "I'm sorry. I really am. I'm very, very sorry. But you know what? She's got more time left than I have. More than anyone on this ship." She takes him onto the ship, the lensflares, in holographic form; Rory transmits the chorus's voices out into the clouds, trying to stabilize the ship, but it's not working. So why are they still singing, then? Why still a silent night? "We haven't told them," ship's captain explains. "I understand you have a machine that controls this cloud layer. If you can release us from it, we still have time to make a landing. Nobody has to die." But everybody has to die, he says, and tonight's as good as any other. "How do you choose?" he asks. She can't answer.
The Doctor met him, back in the crypt, and apologized for it. For taking his heart. For boxing it up in photographs and ice. His eyes were sad, and angry, and full of love. And this is what the old man said: "All my life, I've been called heartless. My other life, my real life, the one you rewrote. Now look at me." But the Doctor wasn't finished with him yet. He still needed to see the future. The old man raged. "Show me! I'll die cold, alone and afraid. Of course I will, we all do! What difference does showing me make? Do you know why I'm going to let those people die? It's not a plan. I don't get anything from it. It's just that I don't care. I'm not like you. I don't even want to be like you! I don't and never, ever will care!" That's why it's cool.
The Doctor didn't believe the old man. Neither did Scrooge. He stood before him, old and alone and lying through his wretched teeth, in the cold, outside Abigail's coffin, and couldn't believe that he'd ever stopped loving. The fish, the sky, the beautiful woman. All these things that meant so much to him, he said he'd one day hate. "Is this who you want to become, Kazran?" The Doctor looked past the old man's shoulder at him, and the old man turned around and when he saw him, he began to weep. They were drawn together, in love and a little bit of fear; he raised his hand to strike and the boy called him "Dad." For a moment, that was what he'd looked like. But only for a moment.
Behind the old man's eyes a dam of love broke¸ remembering Abigail. Remembering Kazran. Half wounded, half in shadow. Gathering the pieces of himself, holding them tight. Begging to be whole.
They rush to the isomorphic thing, now that Scrooge cares again, but he's changed too much. The Doctor's done too much damage, too much healing. He produces his half of the screwdriver but the Doctor can't think of anything for a moment. Until he does: The other half, lodged in a shark high up in the clouds. Resonant. Young Scrooge and Old stay close together as the Doctor works; they stare at each other in blossoming horror and understanding as the Doctor explains their last hope: She will have to sing: "It calmed the shark. It will calm the sky, too." One half battered; one half old and barely living at all. Reaching out across the skies, the years, to heal itself.