It's been four years since Sean Roman (Brian Geraghty) left Chicago P.D., but the former police officer is headed back to the Windy City for a special cause. Wednesday's two-part crossover with Chicago Fire, airing at 9/8c on NBC, finds Roman returning to his old stomping grounds amid a teen opioid crisis involving someone close to him. In light of his personal connection to the case, Roman will seek out help from Fire's Severide (Taylor Kinney) instead of his friends over at Intelligence. Given his abrupt exit at the end of Season 3, Roman's unexpected return will also dig up old wounds.

As you'll recall, Roman's life was in shambles just before his departure. An on-the-job injury forced him into early retirement and Burgess (Marina Squerciati), his girlfriend at the time, decided not to follow him across the country — a move that effectively ended their relationship. Roman was originally intended to return in October's three-way crossover event "Infection," but scheduling issues meant his appearance was pushed to this week's two-way crossover with P.D.

Discover your new favorite show: Watch This Now!

"He comes back to confront the place and the group of people that he has lots of complicated feelings about," Chicago P.D. showrunner Rick Eid told TV Guide. "I think there's a lot of unresolved issues, unresolved anger, and unresolved business, so I think when he comes back for a compelling reason. In the course of dealing with [that] specific reason, his whole life is in evidence."

According to Brian Geraghty, much has changed with Roman in the time that he's been away. While he's still a bit of a loose cannon, the ex-cop has also mellowed out since moving to San Diego. "He's a bit more understanding and not as bull-headed in a way. ... He's older and so he's more reflective," Geraghty said.

Catch Roman back in action in the two-part crossover event airing Wednesday, Feb. 26 on NBC starting with Chicago Fire at 9/8c, followed by Chicago P.D. at 10/9c.

Brian Geraghty, <em>Chicago Fire</em>Brian Geraghty, Chicago Fire