Chicago Fire's Unfairly Written-Out Original Cast Member Makes Their Triumphant NBC Return After 11 Years

Published Oct 14, 2026, 10:00 AM EDT

Alexandria is a British-Canadian writer with a passion for network TV. 
She has a bachelor's degree in computer science from Aston University, Birmingham. After initially working as a software tester, she rekindled a passion for writing and has written for blogs and publications like Hidden Remote, Make a Living Writing, and The Daily Voice. She has interviewed various actors and showrunners, with her most memorably being Tony Shalhoub and Mark-Paul Gosselaar.

When Chicago Fire first started, the cast looked entirely different. In fact, there are just a handful of original characters left, as Chicago Fire season 15 sets up the exit of another, and one of the biggest and most decisive exits came early on in the series.

After already handling the loss of Lauren Graham's Leslie Shay at the start of Chicago Fire season 3, the series decided it was time to write out another character at the end. Peter Mills (Charlie Barnett) said goodbye to Firehouse 51 in a storyline that remains one of the worst Chicago Fire character exits. It didn't fully make sense, but at least there was a chance to see him come back if the situation arose.

That's more and more unlikely now, as Barnett has landed another role on NBC for the first time in 11 years. He plays Jack Hollingsworth on Line of Fire, a character most people believe is dead. That's the story that the parents like to share, but viewers have learned that's not the case at all. It develops an intriguing mystery plot that will carry the show through its first season.

While this doesn't eliminate the chance of Mills returning to Chicago Fire, it does make it a little harder. This isn't necessarily a bad thing, as actors need to move forward in their career, and Line of Fire's acclaimed first season is quickly proving the best place to do so.

Charlie Barnett Returns To NBC 11 Years After Divisive Chicago Fire Exit

It's hard to believe that it was 11 years ago that Barnett left Chicago Fire. It came at the end of the third season, and since then, he has appeared in a handful of shows. He excelled in the two seasons of Russian Doll on Netflix, and most recently, he had a guest spot on Stuart Fails to Save the Universe on HBO Max, but Line of Fire brings him back to the forefront of an NBC series.

It wasn't Barnett's choice to leave Chicago Fire. This came down to a creative decision, with the writers worrying that the cast would become overcrowded and that Mills' development had plateaued. With a natural endpoint for his internal struggles, as he learned more about his father's job as a firefighter and wanted to help his family, the third season seemed like the perfect time to write him out. However, it left a few storylines with loose ends, such as his forgettable Chicago Fire romance with Gabby Dawson.

In the end, Mills chose to leave his job as a firefighter. While he originally wanted to honor his father by becoming a firefighter and joining Rescue Squad, he realized that there was another way to do that. His vertigo made it impossible to be part of the elite Squad, and he saw an opportunity to honor another side of his father's dreams: the family restaurant.

Not only did it leave the relationship storyline open, but it didn't make a lot of sense to see him suddenly leave the career of firefighting. This was the one career he had wanted all his life, and he even overcame setbacks to continue it, when he realized that his illness would stop him from being part of Squad. He was able to pivot, showing just how vital he was to Firehouse 51, and he was always ready to step in to help his Firehouse 51 family, and the show certainly felt his loss afterward.

Why Line Of Fire Makes For Barnett's Perfect NBC Comeback

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While many would likely love to see Mills return to Chicago Fire, Line of Fire has delivered the best possible comeback for the actor playing him. Barnett has another series regular role, taking on an intriguing character with growth potential.

So far, very little is known about this character. He is the son of Peter Krause's Mike Hollingsworth, believed to be dead by the majority of the characters. In fact, even Mike and Jane have started to believe that he is dead, learning that he picked up the last paycheck for the undercover mission he faked his death for a year ago. They haven't realized that he has moved onto another task, which involves other agency members.

The entire concept gives Barnett more to play with, showcasing his acting abilities further than he could have on Chicago Fire. He gets the opportunity to take on different roles within one show, as he takes on different names and jobs while he remains in the shadows on whatever undercover work he's potentially on. He has to hide his real personality as he fits in with the task and undercover character he's creating for himself. It's thrilling to watch him take on a role that could make him the villain.

Can Peter Mills Ever Return In Chicago Fire?

The door was always left open for Peter Mills to come back to Chicago Fire, as his character was able to leave without injury or death. He also left Firehouse 51 on excellent terms, simply choosing to put his family first. However, there is a slight issue with the location Mills moved to.

By moving to North Carolina and leaving the firefighting business behind, a full storyline for Mills' return would be needed. As he chose to leave to help his family, there would need to be a bigger reason for him to come back, even if it's just for a visit. This isn't like when Casey returned after leaving to be in Portland, Oregon, as he and Brett were still in a relationship, and that brought him back.

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There are a couple of ways that Chicago Fire could bring him back, and one of those is coming up with the 300th episode. This milestone episode promises to be huge, with some returning faces, as it could potentially be a turning point for Cruz's exit storyline after 14 years. Mills could come back as another voice to help Cruz see his path — and that there is a life outside of firefighting.

Another way to bring him back would be to showcase that he has a family now. He could want to bring a child to the firehouse that helped him grow up and realize the life he envisioned for himself. However, not only do storylines need to line up, but so do schedules, and that could be difficult for Chicago Fire now that Barnett has Line of Fire.

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  Chicago Fire

  Release Date

  October 10, 2012

  Network

  NBC

  • 

    Taylor Kinney

    Kelly Severide

  • 

    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.

• 

  Line of Fire

  Release Date

  September 21, 2026

  Network

  NBC

  Showrunner

  Joshua Safran

  Directors

  Rebecca Thomas

  Writers

  Joshua Safran

  Cast

  • 

    Peter Krause

    Mike Thornhill

  • 

    Hope Davis

    Joan

  A family of law enforcement officials combine forces across their various departments, breaking necessary rules to investigate a growing conspiracy.