Chicago Med's Will Halstead saw his past as an FBI informant come back to haunt him during the Season 4 finale, leading him to a big realization that might have come too late.
Spoilers ahead for Chicago Med Season 4 Episode 22: "With a Brave Heart"
The high-stakes season finale saw Will (Nick Gehlfuss) be tipped off by his handler — and prospective love interest — agent Ingrid Lee (Anna Enger Ritch) that one of the members of the Burke family that he helped put in jail is being released on parole.
Will wonders if he should be worried by the man walking the streets, seemingly forgetting they once tired to kill him, leading to him being sent into witness protection on the day of his wedding to Natalie (Torrey DeVitto).
Agent Lee tells him that given his history with the Burkes, the best thing for him to do would be relocating out of state and start a new life where he might be safe.
The troubling news comes as Will and Natalie worked together on a case. After Agent Lee gives him the news, Will seems distracted when Maggie (Marlyn Barrett) notices him perusing job listings, but he dismisses her saying he is just curious of the opportunities.
Meanwhile, Natalie's new boyfriend Philip (Ian Harding) admits to Connor (Colin Donnell) that he is thinking of proposing despite them only dating for a short time. Connor hints it might not be the best idea.
After a successful surgery, Natalie and Will bond over being happy for the couple they just saved. Natalie walks away, however, leaving Will wondering what to do next. He meets with Agent Lee outside the hospital and he says he is not going anywhere, refusing to run away.
She says she knows that Natalie is the real reason why he is staying, leading them to break up. As many of the doctors gather for Dr. Charles' (Oliver Platt) surprise wedding, Natalie tells Philip that his daughter is now out of the woods and she will start to grow.
Overjoyed, Philip pulls out the ring just as Agent Lee interrupts and tells her about Will's decision. She begs her to take her ex-fiancé back.
The finale takes a tragic turn in the final moments, when Natalie comes after Will in an attempt to get back together. But they are interrupted by Burke, who slams his car on his and they are both seriously injured. The episode ends with Natalie collapsing in Will's arms.
The big finale moment wraps up the season-long storyline of Will's time as an FBI informant, which all started after the death of his father. At the funeral, one of his friends approached him seeking medical advice, but Will's brother Jay Halstead (Jesse Lee Soffer) enlisted him as an informant to catch the man, who had deep gang ties in the city.
After keeping his ties with the police and the FBI from Natalie, the unfortunate cancellation of their wedding led to their eventual breakup. Will was getting closer to Agent Lee as Natalie developed a new relationship with a new man.