FBI Boss Breaks Down the 'Pretty Traumatic' Maggie Twist That Set Up Missy Peregrym's Maternity Leave

The following contains spoilers from the April 19 episode of CBS‘ FBI.

CBS’ FBI mothership team will be down a key agent for the foreseeable future, due to the heartbreaking and nearly tragic events of this week’s episode.

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The 18th episode of Season 4, titled “Fear Nothing,” found Jubal’s FBI team on the hunt for some sarin gas that had been procured in a deadly meet-up by Hakeen Abbas, a terrorist with a beef against the U.S. government.

Getting a lead on the terrorist’s location at an empty lab, Special Agents Maggie Bell and OA Zidan (played by Missy Peregrym and Zeeko Zaki) — with time of the essence, and unable to wait for proper hazmat gear — split up for a room-by-room search of the facility, tip-toeing over claymore booby traps along the way. Maggie ultimately located Abbas in one laboratory, where she tried to talk him into surrender. Abbas instead attempted to go out guns a-blazing, knocking over a canister of sarin gas after Maggie put a bullet between his eyes. Maggie dove for the canister, but it began dispersing as it hit the floor. Worse, safety protocols triggered the automatic shutting/sealing of the door behind her.

OA raced to the scene, and not a metal chair nor even several bullets could bust the door’s glass. As Maggie succumbed to the toxin and began to pass out, OA scrambled to find any sort of face protection for himself (thanks, construction crew down the hall!), before he rammed a hole into the glass with a fire extinguisher, triggering the door to open back up and allowing him to whisk his partner to fresh air.

Later at the hospital, a worried OA learned that because Maggie had sustained “significant” exposure to the chemical weapon, doctors had only given her a “reasonable chance for a full recovery.” OA, privately at an unconscious Maggie’s bedside, held his partner’s hand and begged to her to pull through, saying, “I can’t do this without you, I don’t want to do this without you.” And, seemingly hearing OA’s appeal, unconscious Maggie ever so slightly nodded, to OA’s delight.

Maggie’s hospitalization and upcoming recuperation paves the way for her portrayer’s maternity leave during the final four episodes of Season 4 — but Peregrym will be back for any potential Season 5, showrunner Rick Eid made clear.

“The reality is that [Maggie’s recovery] is a journey, it’s going to be a while,” Eid told TVLine. “When she does come back, whenever that is, she’ll probably for the most part be the same ol’ Maggie, but she did go through something pretty traumatic. There are not only physical injuries but maybe some emotional ones, and that may affect how she sees the world and how she handles cases.”

When Peregrym was expecting her first child two-plus years ago, Maggie was written off the canvas by way of an undercover assignment; Peregrym then returned for the Season 3 premiere. This time, though, the FBI creatives opted to go with something a bit more dramatic.

“We had a bunch of different ideas circulating among the writers,” Eid says, “and it just so happened we were like, ‘Hmm, there’s this sarin gas idea out there…,’ and it could be an interesting, organic way for Maggie to take some time off. We had a need to find a story point that sent her off for a while, and this one seemed like a natural.”

Maggie’s cheating of death, all as a harrowed OA near-helplessly watched, also set the stage for the partners in crimefighting to come to a new appreciation for their bond.

The scenes between them at breakfast that day, through the laboratory glass, and as OA stood at Maggie’s hospital bedside, were all about “trying to reenforce how important they are to each other, and how much they care about each other,” says Eid. “I was really excited for those scenes, and they both did a great job.”

UPDATE: Watch an emotional Peregrym’s “good-bye” (for now) message to fans:

Now, lest you think that FBI this week depleted its arsenal of high drama, and with four episodes left to go this season, Eid assures that there is more of same to come.

Teasing this season’s finale (airing Tuesday, May 24), “I dare say, it is easily as emotional,” the EP previews. “We’ve got a pretty powerful [Episode] 22.”

Want scoop on one of the FBIs, or for any other show? Email InsideLine@tvline.com and your question may be answered via Matt’s Inside Line.

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