All the worlds and all their differences: she accepted all that a long time ago. The universe had opened like a flower, and all the petals once so closely nestled became fragile and distinct. "That man," he husband had thundered, "that man came and stole our son and destroyed our world."
He was right. Of course he was right. Her son was gone and her grief was written in amber ink across the body of the world. She was not the first mother to wish the world to burn at the loss of her child. She was the first to see it fulfilled. But not the last, never the last.
And so she embraced the notion of difference, of distance, of everything that was hers and everything that was theirs and it allowed her to forget awhile that the man who did not save her son wore the same face in both universes. But in her heart, she'd known the truth: the other Walter had done her husband a kindness in giving him someone else to blame. If he'd just had more time...that's what he told himself, what he told her, but what a beautiful lie.
It saved him. Her husband had not faced the desperate man coming in from the snow. He'd worn a different coat, but he'd loved their son just the same. There were no beautiful lies for her. She accepted difference but she knew that distance was a lie. Each petal is born of a flower, the same flower, and in that way, this broken man before her is her husband just as much as the man she left behind.
And the boy, the wonderful boy, is her son. Born to another Elizabeth, perhaps, but it doesn't matter now. She sees the truth. In all universes, she is his mother. In all universes, he is her son. This will never not be true.
So how can she blame this man for the loss of her son, how can she blame this man who tried so hard to succeed where his other self had failed? The is no meaningful difference between them, no meaningful distance. That was enough to forgive him.
But then he returned Peter, her Peter (for there was never one that wasn't hers) and she got to see him strong, so strong, handsome and brave and grown-
That was enough to redeem them all.