In another life.
It's a dangerous thought, one Peter knows he shouldn't indulge in, but it's all he can think about at 4:00 AM when he's sleeping in a bed that's not as comfortable as hers.
What would have happened if there were no strange cases and she was investigating murders and kidnappings instead of shapshifters and alternative universes.
Maybe in this life he would have actually gone to MIT and his expertise would have aided her in a case. He would have asked her out to dinner and she'd say yes. It'd be easy from there. There would be no crazy fathers, no shared dreams with dead ex-boyfriends, just movie nights and play dates with Ella.
But this Olivia saw the world in black and white. She wasn't open to new ideas or looking outside the box.
This Olivia wouldn't cross universes to save him.
In another life, a life without cortexiphan, Olivia does not become an FBI agent.
They meet in Rome. She's backpacking through Europe, he's there on business. He bumps into her walking out of the Colosseum and she looks like an easy target for a quick con so he takes her for coffee. Somewhere between stories of her trip to Africa and her adventures in college, Peter forgets the real reason he asked her out. He gets lost in her smile and infections laugh.
Their whirlwind romance lasts for only a few weeks. She moves on to Venice and he goes back to his empty apartment in Boston.
This Olivia had no direction, nothing to fight for. This Peter had no reason to stay in one place.
In a life where Walter stayed in St. Claire's, Peter stayed in Iraq. He gets in too deep with a pair of dangerous men and is killed when he doesn't deliver the promised fortune.
Olivia searches for him months later regarding an investigation involving an old business partner, but the search ends quickly. She's the one who tells Walter about his death, not understanding it's the second time the man had outlived a son.
In this world Peter and Olivia never meet. Peter doesn't dream of this life more than once.
Then there's the other life that would have been reality if not for a man's wish to save a boy.
In this life Walter never crosses universes. There's no Fringe Division or Pattern. There's just a man that feels like he was destined for more than being his father's campaign manager.
He meets a beautiful FBI agent one day when she investigates a string of murders of government officials. They meet again a few months later at a U2 concert and go for drinks a few times. The relationship fizzles before it has a chance to take off.
This Olivia seems perfect on paper. She's unburdened, unguarded, and happy. She smiles, and laughs, and says all the right things.
He thinks its strange, but when he closes his eyes he thinks of her as a blond.
He wonders what the Peter from this universe would have been like. If the Olivia from this universe would have preferred the other Peter.
He wonders, if in that life, Peter and Olivia would have fallen together easily. If their relationship would have been perfect. If that Peter would have recognized instantly that the other Olivia was not his Olivia.
When he's feeling really down, staring at the shadows above his bed, he even wonders if he's just a poor substitute for the other Peter, if the Olivia and Peter from this universe are the true tragic love story.
He doesn't like to think about that life very long either.
In this life, when they catch a case and he finally sees her again, he's thankful that this is the life they live in.
He's sorry for her pain and that he caused it. He's sorry he ignored the signs and that the chances of them working it out are slim, but he loves this Olivia Dunham. The Olivia that fights for people, that crosses universes for people.
He'd cross universes for her too.
And the truth is that he knows he and Olivia are meant to be together no matter what universe they come from.