When Peter was a teenager, thirteen or fourteen, he decided he was like a noble gas. He had all the electrons he needed, thanks very much. He didn't need to form bonds with anyone else. He didn't have a best friend at school. "Peter's a loner," a teacher told his mom, but Peter didn't consider himself a loner; he was just sufficient unto himself. He left home at seventeen without a backward glance, and proceeded to not form bonds with people as a lifestyle choice. A complex system of favours owned and owed, yes, but actual emotional bonds, not so much.
In retrospect, Peter thinks, it's probably not surprising. Now, knowing about 1985 and Reiden Lake and what Walter did, a lot of his childhood makes more sense, and he thinks he can remember, like the dark edge of a dream, the sense that this was all wrong, like his entire world was a lie and nobody could be trusted (his mother telling him he had never had bacon). You were very ill might have covered the cracks in the fabric of his reality, but the cracks had always been there. Peter didn't trust anyone.
Peter stood alone.
So, this: here, now, stuck in yet another alternate universe or timeline that is so like his and so utterly not like his, unrecognised and unacknowledged, Peter should be fine. He is alone, but he is made to be alone (he remembers drawing atoms for his chemistry homework and thinking he was like the noble gases). Peter is sufficient unto himself.
But Peter lies on the narrow bed in the cell that Broyles so kindly arranged for him, cold and grey and solitary, with bright dreams slipping away, and thinks that somewhere along the way, he's lost a few of those outer electrons. He's made connections, with Olivia, with Walter, with Astrid and Broyles even, and now he's incomplete.
He misses them. The feeling is like a weight in his heart, and he wants desperately to be back in the house he shares with Walter, feeling exasperated and affectionate in equal measure as Walter potters round semi-naked, feeling flush with contentment as Olivia tucks her feet under his leg while they watch TV. He wants to exchange that wordless, knowing look with Astrid, that look that is shorthand for countless nights in the lab with Walter and endless trips to the 7-11 for red vines. He wants Broyles to look at him and trust him.
Peter wants Olivia's hair to brush his face as she leans in to kiss him.
Peter wants Walter's hand on his cheek as Walter tells him he loves him.
Peter wants his outer electrons back, because he is no longer sufficient unto himself.