Episode 2 of Person of Interest, airing tomorrow night, will delve into Finch's past as well as the origins of the mysterious Machine. And what you thought you knew will most likely change, partly because Reese is making Finch change, as Michael Emerson told TV Guide:
"I thought originally that this is a reclusive character. But he is a far bolder and more active character...Reese has challenged Finch's wall of impenetrability so that Finch now has to be a little more guarded. He has to scramble a little harder to stay a step ahead of Reese."