Hondo reunites with an old flame, FBI Special Agent Elle Trask, when the SWAT team works with the FBI to bring in a separatist group with weapons-grade plutonium. Also, the SWAT team worries they will lose an annual law enforcement charity competition to the Los Angeles Fire Department.

Hondo and the SWAT team race to save Buck, their former unit leader, when he goes off grid and they fear he plans to harm himself. Flashbacks reveal the search for Buck, which coincides with one of the team’s most brutal missions, as each team member receives counseling and discusses the untold mental and emotional difficulties inherent to working in SWAT.

As the SWAT team helps the LAPD search for the prime suspect in a woman’s disappearance, they’re joined in the field by a new team member. The personal strain between Chris and Street comes to a head as both await Hicks’ decision on who the winner is of a prestigious leadership competition.

When Hicks witnesses the assassination of his longtime friend, the team races to find the shooter and determine why he was targeted; Luca struggles with how to help his brother after he's arrested.