As a firefighter candidate, his character starts his time with the show

on the lowest rung of the firefighter career ladder, where he’s still proving

himself worthy of becoming a full-fledged team member. Following in

the footsteps of his firefighter dad, Mills works hard to show he’s capable of pulling his weight at Firehouse 51. Assigned to Truck 81 at first, he will eventually move over to join Lt. Kelly Severide (Taylor Kinney) and the rest of the first responders on Rescue Squad 3. Another move finds him taking on the paramedic role on Ambulance 61 due to a severe injury preventing him from carrying out his firefighter duties. Still, he finally ends up back on Rescue Truck before exiting the show. Through it all, Mills displays an unwavering determination to be a reliable team member of the crew that he admires so profoundly.

In addition, he figures heavily into the romantic element of the show, with an ultimately ill-fated relationship with colleague Gabby Dawson (Monica Raymond). So, with such a pivotal role in Chicago Fire” in its early seasons, it’s perhaps understandable that Barnett took it hard when he was dropped from the cast in 2015. Playing Peter Mills on “Chicago Fire” for over 60 episodes, Charlie Barnett also turned up in another One Chicago show, making four appearances on “Chicago P.D.” His lengthy time on both shows would make the actor one of the franchise’s favorites and a character fans wish would come back.

But despite this, Mills was written off the series in the Season 3 Episode, “You Know Where to Find Me. Speaking with Digital Spy in the aftermath of his exit, Barnett said he initially had no idea how successful “Chicago Fire” would be. “[The show] was a behemoth that I never really saw coming.” He then said how grateful he was to be involved with the series but that his departure from it had a powerful effect on him. “I was really sad to be let go. It broke me for quite a long time.” In the same vein, Barnett took to Twitter at the time to say he was reluctant to go but that he appreciated his run on the hit show, writing, “If I had my way, I wouldn’t be leaving, but I can’t deny the time I had was beyond amazing.” And while he may have been unhappy to say goodbye to “Chicago Fire,” Barnett would soon be saying hello to roles in other popular series, including “Orange Is the New Black” and “Russian Doll.”