On Tuesday's episode of FBI, "Under Pressure," Maggie goes back undercover working at a bar to investigate an anti-government group that regularly meets there and has several members suspected in a series of bombings. The case opens old wounds for her when a single father on the periphery of the group begins to fear he’s in danger of becoming collateral damage.
"It's a really big throwback," Peregrym previewed with ET, which premieres an exclusive clip from the episode (watch above). "When I came back [to FBI] from maternity leave, the storyline was originally that I went undercover, I come back and I have lost my informant and I blame myself that she had died. Being back undercover really brought that up for me. So you see that happen, where I'm really concerned about things going sideways because I feel this heavy burden to make sure that nobody gets hurt for helping us."
The upcoming hour is a significant one for Maggie, whose past traumatic experience Peregrym hopes "makes her a better agent."
"She really cares about people. It's one of the things I really love about Maggie, that she doesn't just do anything and everything to get the win. But there's also the payoff of it. She carries things for a long time when things don't go right," the actress said. "I find that really interesting. It's more fun for me to play as well. It's more stuff for character, that I can have these conversations with O.A. (played by Zeeko Zaki). And he can see that. We do this a lot where we're not sure if the other person is in a good place to make a decision. Or if they're too affected by something because it brings up the trauma of what they've experienced. But it's also the reality of how human beings work."
The FBI franchise also continues to expand and evolve, with Dylan McDermott joining the FBI: Most Wanted spinoff just as Julian McMahon is leaving it. While Peregrym didn't know the inner workings of the casting shift, she expressed enthusiasm over welcoming McDermott -- who recently starred on another of Dick Wolf's shows, Law & Order: Organized Crime -- into the FBI universe.
"He definitely knows the world. I just think it'll be really interesting to see where they take it," Peregrym said. "I'm sure we'll be doing a crossover, and I'm looking forward to being able to work with him and work with the rest of the team, because that really does change the dynamic. When you bring somebody new in, it can change the show. Again, I don't really know what their plans are for that, but I'm sure it'll be entertaining -- and it's always fun to be able to cross over."