Disclaimer: I don't own Fringe.
It was always going to happen, eventually. That one day she'd leave on an operation and never come back.
Broyles assigned another, new agent to work with them after they lost Olivia. Agent Richard Baker swooped in to their lab with proclamations of how things around here were going to run and his way of talking to Walter like a child and making jokes about the friend they'd just lost that made even Broyles scowl in disbelief. And in the end he couldn't hack it. Agent Baker lasted six weeks in Fringe Division, after which Broyles took to dealing with them more directly. Nobody could replace Olivia, so why try.
Walter changed. He retreated inside himself, performing his experiments in subdue and keeping his previously colourful explanations to a minimum. The spirit in his voice disappeared, replaced with something much more penitent. The glint of newfound freedom in his eyes is gone now, too.
It was another year and a half before Astrid left the FBI entirely. She'd seen enough destruction to make her forget why she joined the Bureau to begin with. She retrained as a high school linguistics teacher and moved south to Florida. Occasionally, Peter will receive an e-mail from her, and he and Walter attended her wedding in the summer.
As for Peter? Well, he and Walter are alike in their self- captivity. Which falls under the category of things Peter will never admit, not even to himself. But as well as that, Peter is pissed off at the worlds – both of them – and his anger man itself in mordant remarks and empty whiskey bottles. And more importantly he abhors himself for failing her, a hatred that only intensifies over time.
He wishes he could run away. Sometimes, the urge to escape is so strong that he finds himself looking up flights, but before he clicks 'Book' Peter remembers what it is that keeps him here and that he can't escape his demons simply by getting out of Boston.
Peter trudges through the worst snowstorm to hit Boston in thirty years, effectively shutting the whole city down. Walter tried to convince Peter not to go, to leave it until after the snow passed. It wouldn't matter if he missed it, this time. It matters to Peter though. So keeps his head down as the snow batters his face and keeps his legs so far submerged in ice, he can barely feel them anymore.
Rachel and Ella don't call much anymore, not like they did to begin with. Peter is somewhat relieved; Ella reminded him too much of her aunt.
It's empty of visitors when he gets there. It's hardly surprising given the weather. Nobody wants to battle their way through to visit someone who won't respond back. Even the staff are surprised to see Peter there.
Olivia doesn't respond. As usual, she stares vacantly ahead of herself. Peter doesn't think she knows he's there.
Olivia's blonde hair is long and straggly. It hasn't seen a haircut since she got here. The appearance of patients isn't high on the list of priorities in a mental hospital.
He should've known that it was Olivia's genetic doppelganger that returned with them from the Other Side. He saw the differences, he saw the things that weren't her, yet he couldn't see the wood for the trees. ("You have an IQ of 190, and it took a complete stranger calling you to make you realise you were screwing the wrong me?")
They both got back to the correct universe, but the Olivia Dunham that Peter knew never returned from the Other Side.
Olivia's unravelling was gradual, so gradual that nobody realised she was losing her mind until she did.
Peter should have noticed. He failed her by leaving her over there, and he failed to see just how much damage Walternate had done to her until it was too late.
When Olivia was first admitted here, Peter could still converse with her. Sometimes he'd speak with his Olivia. Other times, he'd speak with the one that Walternate injected her with. Occasionally, Olivia would speak with Charlie or Frank. Now she doesn't speak at all. Peter hasn't heard her voice in over a year.
Olivia sits there, barely existing, a hollow shell.
So Peter talks for both of them. Today he tells her about the snow. She hates the snow, so it's just as well she's stuck in here. Or at least she used to hate the snow. Peter tells her about the latest case they're investigating (even if the cases are mellower since the universes battle ended.) She would have had it solved in thirty seconds.
"I miss you," Peter tells Olivia. "It's not the same without you around. I've got nobody to give my 'Walter is crazy' looks to. "
Olivia blinks. Peter stopped trying to read her eye movements as signals a long time ago.
"He asked me to tell you hello from him. He'd visit himself, but a mental institute is last place he needs to be."
How the hell did Walter become the saner of the people Peter cares about?
Two of the other inmates/residents/patients/whatever you want to call them (Peter has given up on finding the right term) begin to fight with each other, and the crash of one being thrown to the ground makes Peter jump in his seat. Olivia doesn't.
Peter glances to the window. The snow is falling more heavily than it was when he left, and the sight of six institute staff grappling to restrain and sedate the fighters isn't something he wants to see. He won't be able to get the image of one of them attacking Olivia out of his head.
So he tells Olivia that he has to go before Walter does something Walter-like (or at least the- Walter-she-would-remember-like). He'll be back again next week.
"Take care of yourself, Liv," Peter says, trying to ignore the pain in his throat he always gets at this point. He takes a last look at Olivia. She hasn't moved an inch since he got there. She never does. "I'll see you later."
She blinks again, and Peter makes his way out of the hospital, back into the snow.
If Peter's being honest with himself, he always knew Olivia would give up her life for the job. He just didn't think it would be like this.