Three of the four involved captives. Miles and Monroe are captives in Mexico, where the people are singing "Born to be Wild". Charlie and grandpa get taken into custody by the Patriots, as Charlie tries to do her best for grandpa on a foolish mission to save an old friend, who, unbeknownst to Grandpa Gene, is already dead. And back East, Jason gets himself taken into custody, presumably because he broke into his mother's new man's room, he being Chief of Staff to the President of the reconstituted United States.
The reason Jason did this has to do with one of the unifying roots of the four stories: the Patriots are implementing the beginnings of some kind of germ warfare to cement their hold in the new United States. That's what killed Gene's old friend. Presumably the Patriots will give the vaccine to themselves and their loyalists, and wipe everyone else out. This will be the scene in Texas - the Patriots ready to strike - that Miles, Rachel, and Monroe, now joined by his son, will be returning to. The Mexican thread, which gave us some good scenes with Monroe and his son Connor, should now fade into the past.
The standalone thread entails Aaron reunited with his wife, and learning much more about the nanites. As Grace explains, there are more nanites now loose on this planet than neurons in our brain. They've begun to band together, to the point where they constitute a mind of its own, which, as Grace suggests, makes them equivalent to ... God.
It's a nice science fictional move, and it will be interesting to see if this new uber-Mind has an opinion about the Patriots.
And see also Revolution: Preview Review ... Revolution 1.2: Fast Changes ... Revolution 1.14: Nanites and Jack Bauer ... Revolution 1.15: Major Tom and More 24 ... Revolution 1.16: Feeling a Little Like the Hatch in Lost ... Revolution 1.17: Even Better Nanites ... Revolution 1.18: Whodunnit? ... Revolution 1.19: Cheney's Bunker ... Revolution Season 1 Finale: Good Pivot