2. Season 2
Elite television right here. Season 2 had one of the show’s very best storylines, which involved an arsonist who turned out to be a former firefighter. The writers did an excellent job of taking what worked in the first season and amplifying it, whether it be the interactions between characters or the types of calls the 51 would get.
Nothing in season 2 feels overwrought, which is an issue that some of the later seasons ran into. Every note hits the right level of seriousness, and the screen time dedicated to each character lets us into their world in a satisfying and entertaining manner.