By now we know that Mr. Finch built and designed the software that finds the titular 'Person of Interest' (Thu., 9PM ET on CBS) in each episode. His guilty conscience about these people who aren't tied to terrorists but still in danger lead him to seek out Reese and start this clandestine operation they've got going on.

But it wasn't always that way, as we saw in this week's flashbacks. We also saw Finch running on a treadmill, so the injury that's lead to his current limp and limited mobility happened after this -- perhaps when he stopped working for the government?

Mr. Finch had a cohort while designing the software, and it was this man who was first horrified by what Finch called the "Irrelevant List." He asked how they could live with themselves knowing those people are in trouble.

This is why Finch designed the system to purge the Irrelevant List each night. "We didn't build this to save somebody," he said then. "We built it to save everybody."

Obviously, Finch has completely reversed course with his stance on this issue, as he's now working outside the system to save the very people he was eager to dismiss. How he went from that man to the man we know now remains to be seen.