So, the theme of this episode was finding out what makes people or machines tick.
Ellison is driven by the desire to understand his role in all this and to find a way to actively fight the coming Armageddon. He thinks by delivering Cromartie's body for analysis he'll contribute to that end, so he hides his actions from John. Trying to "fight" on his own as he wasn't invited to fight with the Connors.
In the scenes with Cameron and John we see Cameron trying to understand feelings, emotions; testing them and herself really. As she says, she wouldn't be worth much if she couldn't feel them. That brings the question, worth much to whom? John, herself, the machines?
Derek and Jessie's story revolves around a machine collaborator who has come back from the future. Derek learns about some missing weeks or months he has spent tortured by this individual as a subject to teach the machines to appear more human. Derek still can't remember this time but finally believes Jessie it really happened and then Charles Fisher (the elder) confirms it). Derek shows his understanding of people under extreme stress himself when he doesn't try to get the elder man to talk by torturing him directly but by doing this to the younger version of the man. He wants to get to the reason of Charles Fisher's appearance back in time and later wants to prevent him from coming into being as a traitor to humanity by killing the young man. But in both cases Jessie interferes and finally kills the old guy and shows a surprising lack of interest in what happens to the young one. They let that one go and future history repeats itself (how is that for a paradox).
Again, they let someone who has learned about the future just go on his way, not trying to bring him in, not killing him to prevent him to becoming a traitor, nothing. Weird, to say the least.
And still, Derek keeps his life and Jessie separate from the Connors, not really working together for their supposed common goal.
And of course Sarah being ill goes into her own subconscious to figure out what makes herself tick. She even seeks out the psychiatrist again to help analyze her dreams but since she can't reveal her life she has to figure it out by herself. Ultimately it leads her to the blood writing in their garage (or whatever). So, some warning of some kind, but she and later John can't yet see what the three dots that were repeatedly in her dreams and she found on the wall later on, where all about.
There is an unfortunate tendency in all people involved to "go it alone", keep things to themselves and thus to be integral in bringing about what they fear. Very human I'm sure, but in the face of what they know will happen if they don't prevent it and unite against the threat, still rather disturbing.
So, I guess, the story is evolving at an accelerated speed it certainly makes me want to keep watching and at the same time frustrates me with people working more against each other than with each other. Guess, that's good television..