When Hondo’s imprisoned childhood friend asks him to protect his son from gang violence, the favor brings SWAT into contact with a new local crime outfit. Also, when Luca’s grandfather, a SWAT legend, passes away, he struggles with his grief and a painful family secret.

The SWAT team works together with former member, Jim Street to find a woman and her son who are running from an international drug cartel. Hondo makes a distressing discovery about his incarcerated friend’s teen son. Luca mulls over a government program that allows officers to buy homes in the at-risk neighborhoods they police.

Mumford returns to work a 15-year-old cold case that holds a personal connection and leads to the discovery of a dangerous drug ring. Hondo is leery of Leroy’s motives when he discovers the recent parolee is seeking funding for a new business venture with his son, Darryl.

As the team works to stop a violent attack on the city, they're forced to confront the group responsible for the death of a team member. Hondo and Leroy disagree on how to handle a challenge to Darryl's fledgling business.

The team races to rescue victims of a sex trafficking ring that is preying on disenfranchised women. Also, Hondo finds himself at odds with Leroy and Darryl over the future of their business, and Street confronts Chris about meeting with his hospitalized mom.

The bombing of a Los Angeles police station puts the city on edge, leading the team to a final showdown with a group of domestic extremists. Also, Hondo faces the fallout from a bold decision that threatens his future, and Tan takes a big step in his personal life.

The SWAT team partners with the DEA to locate stolen rocket launchers smuggled into Los Angeles, high-power weapons with new technology capable of cutting through armored tanks. Also, a personal issue for Tan arises when a colleague is hurt in the field; Hondo's inquiry into the arrest of a homeless veteran for Leroy, Darryl's father, sparks an idea for a new policing initiative; and Luca suspects the mother of his mentee, Kelly, wants to date him.

When a home invasion turns deadly, the team embarks on a race to track down priceless antique artifacts before any more lives are lost; Leroy enlists Hondo's help after an overdose hits close to home.