Founding One Chicago Cast Who's "Super Frustrated" To Leave Backtracks Stance

Published Oct 26, 2026, 12:30 PM EDT

Laura Hurley has been writing about the entertainment industry for more than twelve years, after a decade as a content producer and editor at CinemaBlend after writing for WhatCulture and Examiner. Attending events like SCAD TVfest and San Diego Comic-Con over the course of her career, she has been immersed in the world of network, streaming, and cable TV. 

NBC's One Chicago franchise has run for a total of 800 episodes across four shows so far, and plenty of actors have come and gone since Chicago Fire first premiered in 2012. The founding series is just weeks away from saying goodbye to one of the original first responders after 15 seasons, but another original cast member has opened up about wanting to come back to Firehouse 51. In fact, he changed his stance on his character's fate to the point that he has ideas about what could bring him back. Charlie Barnett sees a future for Peter Mills.

Barnett was one of the earliest members of the Chicago Fire cast, starting out as a CFD candidate who was placed at Firehouse 51. He appeared in a total of 70 episodes between Chicago Fire and Chicago P.D., and his exit was one of the first major departures in the entire franchise. Fortunately for the actor, Mills wasn't killed off like Lauren German's Shay was, so the door has been open for him to return since 2015. That return just hasn't happened yet by this point in NBC's 2026 fall schedule.

The timing has never been better, and not just because of Joe Miñoso's upcoming exit as Cruz. Barnett is back on NBC as part of the cast of Line of Fire, the network's newest hit drama, so he's a familiar face on the network yet again. That doesn't necessarily mean he can drop by the Windy City to don his Chicago Fire turnout gear at any moment, but the actor's comments about Mills this fall bode well.

Chicago Fire's Charlie Barnett Softens Up On Mills' Exit Story

Despite his status as one of Chicago Fire's most important characters early on, the drama went in some wildly different directions for Mills over the course of just three seasons. He started out as a candidate under Casey's command on Truck 81, then moved over to Severide's crew on Squad 3. An illness then benched him from active duty as a firefighter, sending him to work on Ambulance 61 with Brett. Then, he eventually moved back to Squad 3, before deciding to leave the CFD altogether and return to North Carolina to help run the family restaurant.

While he wasn't killed off like Shay, Mills was gone for good after the season 3 finale, and he didn't get a particularly climactic end. Charlie Barnett was open about his dissatisfaction with being written out of what was then one of NBC's rising hits, as well as with why Mills decided to leave his Firehouse 51 family. Speaking with TV Insider about returning to NBC in 2026 for Line of Fire, Barnett acknowledged his lingering frustration:

I was super frustrated to leave the show. I’ve said that very publicly. I did not want to go. I wanted to stay there. I was very excited to be a part of that crew and that community. But when I left, when they wrote me out, I was even more frustrated that Peter Mills wasn’t going out in a blaze of glory. Literally, I wanted him to throw a baby out the window and burn in the… You know what I mean? I wanted it to be epic, like Peter Mills is a god. And they were like, ‘No, you’re just going to go to North Carolina and start working with your mom in a diner.’ It’s like, ‘OK.'​

It likely didn't help that other characters did get to go out in a "blaze of glory," more or less. Shay died in a crisis early in season 3, while Otis was killed in a fire to start season 8. Other characters, like Casey at the end of season 5 and Cruz at the end of season 14's life-or-death cliffhanger, nearly got to go out in spectacular fashion as well. Mills just left to go to North Carolina, and never came back. Barnett has now backtracked enough to find a silver lining:

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I look at that, and I’m like, ‘Well, shoot, Peter Mills is still working at that diner, so when is he going to get the itch again?’ I’m imagining, and I want this validation of him being like, ‘I’m called again. This was my father’s…’ Peter Mills’ dad was lost in [a fire], and that’s why his mom is trying to pull him away. It’s a deeper connection for him. It’s a deeper responsibility that he’s been away from for so long. I kind of envision him having, in North Carolina, already joined a force down there and he’s doing his own work, and somehow it’s going to bring him back up somehow. I’ve been working out. Let’s get this.

According to Barnett, Mills leaving the CFD to help his family with the restaurant in season 3 doesn't mean he permanently gave up on fighting fires. After all, North Carolina has fire departments that he could have joined. Gallo, Carver, and Casey all simply joined departments in different cities when they left; Mills could have done the same between the end of season 3 and Chicago Fire's current fifteenth season.

What's The Best Way To Bring Back Mills (& When)

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Charlie Barnett coming around to the idea of returning to Chicago Fire doesn't mean that Mills will be back. The actor is part of the cast of Line of Fire, the drama that marked Peter Krause's triumphant return to primetime after his character's tragic fate on 9-1-1. While Barnett isn't one of the leads, Line of Fire isn't slowing down. NBC has added 5 more episodes to the first season, bringing the total up to 18. That likely means that Line of Fire will wrap season 1 in the spring, like the One Chicago shows, rather than in midseason.

Barnett may simply be too busy on Line of Fire to rejoin Chicago Fire any time soon. That said, Line of Fire films in New York City, so the productions aren't nearly as far apart as if one filmed in Los Angeles. Both shows airing on the same network surely wouldn't hurt the odds for the actor. With Line of Fire now running for 18 episodes rather than One Chicago's usual 20+ episodes per season, he could have time towards the end of season 15. Line of Fire will presumably wrap before Fire does next year.

Plus, Chicago Fire has set a precedent for bringing former stars back as guests for a single episode or short arc. Jesse Spencer reprised his role as Casey for four episodes after exiting in Chicago Fire's 200th episode, starting with the explanation that he had to come back to the Windy City as part of a task force.

Monica Raymund returned for a single episode of season 8 when Dawson was raising money for aid in Puerto Rico. Alberto Rosende's Gallo briefly returned in the season 12 premiere before relocating to Michigan to join Detroit's Fire Department, while Jake Lockett's Carver came back for a full episode of season 14 despite joining the Denver Fire Department in Colorado.

The best way for Chicago Fire to bring back Mills would be to follow Carver's path. Even though Carver left for very different reasons than Mills did, the One Chicago drama found a convenient way to organically bring him into the fold for a single episode. Carver came back to Firehouse 51 when he got word of Violet's paramedic training program for firefighters, and checked it out for himself to see if it would be a viable program for him to bring to Denver.

While Chicago Fire is running out of firefighters from the first three seasons for Mills to reconnect with, the show could set up a twist in Chicago that would draw him back to the city to see if it could apply to whatever work he's doing in North Carolina. The approach that worked for Carver would be a brief but logical way to feature Barnett as Mills for the first time since season 3, without conflicting with his duties on Line of Fire. For now, however, the biggest event on the way to Chicago Fire is the upcoming 300th episode.

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  Taylor Kinney

  Kelly Severide

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  David Eigenberg

  Christopher Herrmann

Chicago Fire follows the lives of firefighters, rescue squad members, and paramedics of Firehouse 51 in Chicago as they face professional and personal challenges, showcasing their dedication, teamwork, and resilience.