Warning: moderate spoilers for tonight's episode of "Fringe" lurk ahead.

Scene from "Fringe" episode "Peter"

Dr. Walter Bishop (John Noble) has a secret - a secret so dark that if anyone discovered it, his life and the lives of those closest to him would be tarnished forever. Unfortunately for Walter, but fortunately for "Fringe" fans, that secret is about to be revealed.

In tonight's installment of "Fringe," Walter finally reveals to Agent Olivia Dunham (Anna Torv) the truth about his son, Peter (Joshua Jackson). The episode, aptly titled "Peter," travels back to the 1980s when Walter's young son died of a mysterious illness, resulting in a series of events that culminates in the abduction of the alternate Peter that viewers have come to know.

"It's quite interesting having played Walter 25 years younger; he's actually quite a likeable man," John Noble told CBR during a group interview on the Vancouver set of "Fringe." "But he does make choices, that one error that causes this tumbling effect, the poor lad. All he was trying to do was play God, really. 'Oh, I can fix this boy.' In fact, he [tells his assistant] that there's only one god in this laboratory, and it's not yours. That's quite an interesting thing about Walter - he's mentioned that a few times. So he played God...and of course, it ruins both of their lives."

Walter's secret will make itself known as the rest of the season progresses, and the results are far from pretty. In fact, the only person even remotely sympathetic to the very broken Walter is Astrid Farnsworth (Jasika Nicole), an FBI agent and Walter's frequent laboratory assistant.

"Astrid doesn't have this history with Walter...so it makes sense that she comes at it with a fresh perspective," said Nicole of Astrid's response to Walter's revelation about Peter. "But at the same time, she could easily have said that this wasn't in her job description and she doesn't feel comfortable doing this and she could have been assigned to something else, but she didn't want to. There was the seed of something special there; she respects him and appreciates him.

"When this whole thing with Peter blows up, everybody will have separated from him and they're upset with him," she continued. "They can't believe he did this. He's so apologetic and he wants to right his wrongs, but he can't. What can you do in that situation? Astrid just wants to be there for him. That was a nice build to show how important she'll be to him in the future once he's kind of abandoned and not surrounded by Olivia and his son. She's there for him."

Scene from "Fringe" episode "Peter"

"You'll see her looking out for Walter in a way that no one else will, in a truly beautiful and unconditional way," Noble agreed. "I think Olivia has great care for Walter as well, but of course with Olivia being stitched up emotionally, she can't show it. But we have some beautiful moments, Astrid and I, which you've seen some of already. That will continue. It's a relationship that will continue to grow."

Sadly, Walter's relationship with his son won't fare quite as well, at least for the time being. "It was difficult," Noble said of the inevitable confrontation between his character and Joshua Jackson's. "Certainly, it's horrible. It was very difficult for Josh and I, because we like each other as men. But we did it full on."

But even if their relationship is headed for a rough patch, Noble is optimistic about the future of Walter and Peter, despite the elder Bishop's morally ambiguous decision. "Like a beautiful vase that gets broken, [their relationship] will be repaired by a master repairer," he said. "There is a breaking apart and a slow mending. I don't know how that mending is going to take place, but sometimes things that are mended are stronger than they were before they were broken. That's the feeling that I have with that relationship."

Before any reconciliation, however, there's another character to consider in the equation - Peter's real father, the alternate Walter Bishop, referred to by both the show's crew and the characters themselves as Walternate. Walternate first appears in tonight's "Peter," and he'll resurface later this season in a rather prominent way.

"You'll certainly see more of him," said Noble. "In the finale, you'll see an awful lot of him. Again, it's a challenge and it's the same man, but with different choices made in life. We also talk about that on 'Fringe,' don't we? The parallel universes, the choices we make will impact how we turn out in life. Walternate is in a different profession than Walter, a high power position. He's a very powerful man. I can't really say more than that, but he's... very interesting."

Tonight's all-new episode of "Fringe," titled "Peter," airs on FOX at 9:00 PM EST/PST and 8:00 PM central. Stay tuned to Comic Book Resources in the coming weeks for more from our visit to the "Fringe" set in Vancouver!