The SWAT team works with Lieutenant Piper Lynch, a senior LAPD Hollywood Division officer, when the mayor assigns her to oversee city departments joining forces to stop a serial bomber using drones as detonation devices. Just as Hondo settles into legal guardianship of his teen charge, his home life becomes more complicated when his estranged father unexpectedly moves in.
Lynch pulls the SWAT team's focus when the mayor tasks her with enacting a departmental review of the squad right as they pursue the unstable and dangerous fugitive leader of an infamous doomsday cult. Luca asks the team to invest in his new passion project-a Guatemalan food truck.
The SWAT team bumps heads with Lynch when she signs them up for an off-book undercover operation to take down a local gang printing counterfeit money, without giving them enough time to prepare for the mission. Tensions rise at home for Hondo as his parents' strained relationship becomes worse.
Deacon's family gets caught in the crosshairs of a drug cartel when the team aims to bring down its leader; Hondo receives troubling news regarding his father; Tan is forced to go before an internal review board due to his girlfriend's indiscretion.
Street reconnects with his estranged foster brother to help a joint investigation between SWAT and the Long Beach PD when criminals steal a mass arsenal of LAPD assault rifles. Hondo finds himself at odds with his father over the elder man's declining health. Luca is overwhelmed when the entire team reconsiders becoming investors in his food truck.
The Harrelsons engage in a tense family reunion when Hondo's older sister, Winnie, begrudgingly arrives in Los Angeles to see their sick father for the first time in decades. The SWAT team searches for an abducted Middle Eastern human rights activist. Luca's food truck business hits a snag. Street worries that dating Captain Hick's daughter, Molly, will negatively impact his career.
The SWAT team searches for thieves who are on the run with a high-tech thermal lance that can cut through almost anything. To find the thieves, SWAT works to identify their target. Also, Chris confronts an imbalance in her relationship with Kira and Ty.
The SWAT team engages in tense negotiations with a family that takes a local officer hostage when they're evicted from their home due to eminent domain. Also, Hondo reflects on his personal life choices as he helps his father through a medical crisis and Chris' relationship with Kira and Ty reaches a critical juncture.
The SWAT team joins forces with the Los Angeles Organized Crime division to recover an officer abducted during a failed undercover operation. Also, Chris struggles with how to comfort the kidnapped officer's parents when she is restricted from giving them certain details of the investigation.
The SWAT team's task to provide security for a warlord is threatened by assassins determined to take him out before he's extradited by the International Criminal Court. Also, Hondo's father, Daniel Sr. tries to make amends to his mother, Charice. Street's foster brother, Nate asks for his help with a corrupt boss and Deacon reluctantly explores therapy for his daughter, Lila.
Street is caught between his duty to SWAT and his commitment to his foster brother, Nate, when Nate is ensnared in a criminal enterprise that could ruin them both. Also, the SWAT team goes after a ruthless crew that uses deadly force while stealing from card casinos, and Buck approaches Deacon to partner on a private security opportunity.
Hondo and the SWAT team rally to support Street when he puts his life on the line to help his foster brother Nate break away from a drug ring.
Hondo, Deacon, Tan and Commander Hicks engage in a manhunt across Tokyo when they escort an extradited fugitive to Japan, where he escapes local custody. Back in Los Angeles, the rest of SWAT search for any contacts the criminal cultivated while hiding out in Los Angeles, and Street isolates himself from the team as he deals with family issues.
The S.W.A.T. team searches for a link between the seemingly unconnected victims of a lone gunman targeting women. Also, Luca assists with a hugging investigation in his neighborhood; Lieutenant Lynch pushes Chris to do a news interview; and Hondo reaches a juncture in his relationship with Nichelle.
Deacon's second job working private security at a high-profile boxing match places the SWAT team in the middle of a kidnapping case when a prize fighter's wife is abducted. Also, Hondo's young charge, Darryl, becomes frustrated with his lack of paternal rights regarding his infant son, and Tan prepares to introduce his critical mother to his girlfriend, Bonnie.
The SWAT team's search for an abducted teen leads them to a member of the Witness Protection Program and a decades-old political extremist group. Hondo and his girlfriend disagree over a guest speaker at her community center. Luca worries he's not physically ready to return to the field. Commander Hicks reconnects with his estranged son.
The SWAT team must protect a hotel full of civilians after a joint task force mission with the LAPD Gang Division goes wrong, and the city's most dangerous gang leaders scatter across the building to find an escape. Also, Luca's efforts to coordinate the team's mission are complicated when his brother, Terry, a freelance stringer reporter, crosses police lines to shoot footage.
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.
The team searches for an escaped convict who plans to hug Tan and every member of law enforcement who helped put him in prison years ago. Chris comes face to face with internal corruption when she arrests a young man who is given a free pass due to his powerful father, and a surprise visit by Hondo's sister, Winnie, puts pressure on his relationship with Nichelle.
The team pursues a couple reminiscent of Bonnie and Clyde, when the duo goes on the run and on the hunt for a set of rare chest pieces worth millions. Hondo and Darryl are surprised when Darryl's ex-girlfriend visits with his young son. Luca confronts his fear of failing his re-qualification to return to the field as he helps Kelly, his mentee.
The team searches for a group of drug smugglers who crash a plane and scatter after a joint mission with the DEA to stop the shipment goes awry. Hondo tries to make amends with Nichelle. Luca experiences anxiety about his return to the field.