The episode in which Buck and Tommy reach a significant relationship milestone— something like moving in together, telling each other "I love you," having a first anniversary, or a casual proposal— should be titled "The Butterfly Effect."

Part of the episode's A-plot would consist of Tommy having a close call during an emergency— after which it is revealed to Buck that Chimney saved Tommy's life after Tommy jokes that he's glad he's okay because Chim's not around to save his ass anymore (Chim then brags about how much of a hero he is and how, if not for him, Tommy and Buck would never have met)— and of Maddie and Jee-Yun running errands all day, with Maddie doing little things to help others. The emergencies would center around narratives about how just one small change would have prevented the 9-1-1 call. One woman at a scene remarks that if "that woman" (Maddie) hadn't helped her earlier, it would have been her on the way to the hospital instead. Near the end of the episode, Buck and Tommy visit Maddie, Chim, and Jee-Yun (maybe for a family dinner or something). Jee-Yun almost has a terrible and very serious yet banal accident (like falling or hitting her head), but Tommy steps in on time and stops it. Chimney realizes that if he had never saved Tommy all those years ago and introduced Tommy to Buck, his daughter's fate at that moment would have been very different. The episode then ends with Buck reflecting on the significance of his relationship with Tommy and how much he means to him. The two men then decide together to take "the next step" in their relationship.

Just one small change. Tommy would have died. Buck would not have begun at the 118 (that vacancy would have been filled well before he left the academy). Chim would not have met Maddie. Jee-Yun would not have been born. There would have been no cruise ship rescue. Buck would never have met Tommy. And everyone's lives would have looked a lot more like those in Buck's coma dream.