Finch looks thoughtful for a moment, then starts talking. Because right now, while they have a murder to stop, is an excellent time to exposit the backstory JC's been wanting since Day One. Finch says that when the towers came down -- and so we know how creepy he is, he says, "when you were in a hotel in Mexico" -- Finch was here, working. He didn't even know about the attacks until that evening. He had spent the better part of his life making himself very rich, but suddenly the money didn't amount to much. They literally stroll through the park like a couple of lovers -- Finch with an unexplained limp -- as Finch continues that the government gave itself power to listen to every cell phone and read every email, but they needed something to sort through it all and pick out the terrorists. The public wanted to be protected, but they didn't want to know how. So when the government finally got a system that worked, they kept it secret. Finch built that system.
But there was a problem: He built it to prevent the next 9/11, but it was seeing all sorts of crimes. So he had to teach it to sort out "irrelevant" crimes from "relevant" crimes. Surveillance cameras watch them walk, as he says the machine erases the irrelevant crimes -- those that won't cause massive loss of life -- every night at midnight. Later, those irrelevant crimes started to eat at Finch, though. JC asks where the machine is, and Finch says the drives are in a government facility somewhere. But the machine is everywhere, watching us with a thousand eyes and listening with a thousand ears. Surveillance footage and sound. Finch built himself a backdoor into the machine, because he figured he needed to be able to shut it off if the government got too powerful. And he uses that to get the irrelevant list. Just Social Security numbers so no one catches on. So he says he doesn't know anything more about Diane Hansen, but the machine wouldn't be steering them toward her if something wasn't going to happen. JC doesn't know if he can protect her because he can't see the whole picture. Finch says he offered JC a job; he never said it would be easy.
Carter shows up to work and a fellow cop tells her about Anton and his friends getting shot by "one guy, in a suit" while trying to buy guns. She looks thoughtful. Not really a very big role for an Oscar winner, is it? Considering how upset she was that she wasn't in the promos, especially. Nothing against her, but this really feels like a two-person cast -- at least so far -- so her complaints seem unwarranted.