In season one, we shift between flashbacks of the captives and follow OA and the crestwood five within the same dimension.
In season two, we shift between the five in dimension 1, and OA and the captives in dimension 2.
In season three, we can have a shift between Karim in dimension 2, and everybody else in dimension 3. OA has to have a ‘brother’ in 3 as well, who could be a new character unconnected to both her family-groups like Karim and the FBI officer were.
We know that OA wakes up as Brit, who is married to Isaac (Hap) and is working on a show with the same storyline in this third dimension. We know that Steve and Buck are also on the set. When OA falls after the dimensional travel, Hap and Steve both get into the ambulance with her. Steve somehow knows that that is Hap (as opposed to like, Homer? How?) and lets him know that.
We’ll start building the story from here.