Haha, knew you'd all be freaking out when I logged in today. That was an intense ride, and as Error said right above me, an amazing ep just to see Samaritan getting in on the action. I was freaking out the whole time. I have to imagine the show is only ramping up Samaritan as the ongoing villain at this point (no way do all of these loose threads resolve in three episodes; even this episode is still introducing new pieces, like the briefcase) so I'm looking forward to more of that, for sure.
I loved how this one tied back into earlier stuff like the stock market crash, and contextualized so much of what has happened so far as part of Samaritan's plan to hunt down the Machine. My prediction for S4 was that the Machine's location would be a major plot point again, so it was great to finally see what had been going on there. And that damn tease at the end, wow. Not on any networked device in the world? Are we still going with the prevailing theory that the Machine is everywhere now? How is it hiding from Samaritan?
Also, damn cool to see Zoe again, and only a few episodes later. It's a small bit but touches like that really made this episode feel like classic POI. "I know it's bad but it's not Zoe Morgan bad" made my whole night. Great line. In a season that, nearing the end, has proved hit or miss for me, I'd easily call this one of the best episodes.
My current top five for S4 as we approach the end:
1. If-Then-Else
2. Control Alt Delete
3. The Devil You Know
4. Search & Destroy
5. Prophets