(S02E18) "Until I took my son from the other side, I had never believed in God. But it occurred to me that my actions had betrayed Him, and that everything that happened to me since then was God punishing me. So now I'm looking for a sign of forgiveness, a specific one, a white tulip ... If God can forgive me for my acts, maybe it's in the realm of possibility that my son will be able to forgive me." - Walter Bishop to Alistair Peck

First of all, how cool was it to see John Noble and Peter Weller hobnobbing on screen together? Just two old scientists exchanging time travel theories and comparing notes on saving/stealing loved ones.

It was the perfect vehicle to build on Walter's struggle about whether to tell Peter or not. In a sense, he'd already been through what Alistair was contemplating. Yes, Walter had crossed to another universe while Alistair was trying to jump back in time, but the result was the same -- be with the person you'd lost. Anyone who's lost a loved one can relate. There's nothing you wouldn't do to be with that person again, even if it means jeopardizing others in the process.

How do you catch someone who can alter time itself? That's the question on the latest episode of 'Fringe' (Thu., 9PM ET on Fox). Alistair Peck (played by guest star Peter Weller) is a scientist with a troubled past. He has the ability to travel through time, and he wants to use this power to save his wife from a deadly accident. Unfortunately, by changing past events, he puts the lives of even more innocent people at risk.

Watch the video after the jump.