Muzzle

Jake Rosser and Ace patrol a LAPD neighborhood when headquarters reports a disturbance. Ace detects cocaine inside the trunk of a stolen car, confirming the officers' suspicions of illicit activity. They open the trunk and secure the evidence as they prepare to pursue the suspects.

An inspector confirms the suspect has fled the scene, forcing a wider street search. Jake teams with Ace to comb city streets for any clue linking the car to the wider drug operation. The tension mounts as the team presses deeper into the search.

Ace detects a clue near a makeshift tent, drawing the team in. Gunfire erupts from inside the tent, and a nearby officer inadvertently touches a cocaine packet that detonates a bomb, blowing up a car. Jake and Ace are forced to chase the fleeing suspect into a nearby under-construction building.

A gunfight erupts as Jake corners the suspect, who dies in the exchange. Ace is grievously wounded in the chaos, and medical staff struggle to save him while the situation deteriorates. Jake lashes out at the medic after Ace is overlooked, and the dog dies; he attends Ace's funeral and is left devastated.

Back at the station, Jake is interrogated about the events and faces pressure from his peers who question his judgment. He asks for Ace's autopsy report and even hints at pursuing a homicide case against the suspect. The strain pushes him toward quitting the force.

Ramos introduces Socks as a new canine partner for Jake. Jake visits Leland's kennel, bonds with Socks, and brings her home, where the traumatized dog gradually starts to respond to him and form a connection.

With Ace gone, Jake is suspended and sent to therapy to cope with his grief. He begins dating Mia, and the therapist eventually clears him to return to the squad if he stays on track. Ramos warns him to stay focused and not go too hard without the team.

Back on duty, Jake trains Socks, who initially ignores commands and bears visible trauma (including her titanium tooth). A breakthrough comes when Jake accidentally snaps his fingers and Socks masters the drill, revealing a growing bond and trust.

Ramos ties a drug bottle symbol to Xiang Xi, a Chinese manufacturer; Dante recalls Socks and points Jake to a gated, posh area. Jake and Socks confront the dog and its owner, who also commands his dog in German; a deadly confrontation ensues with both dogs killed.

Ramos confirms a car registered to Xiang Xi connected to the fentanyl operation. Jake and Socks infiltrate a fentanyl production building, but he is knocked unconscious and fentanyl floods his system. Cartel members take Socks and coerce her, leaving Jake adrift and disoriented.

Jake learns from Santiago, Socks' former owner, how the cartel drugged and stole dogs to hide their shipments. With this history, Jake understands Socks's fear of the drug bottle and becomes even more determined to save her and strike at the cartel.

Jake fights through the cartel's stronghold but is forced to surrender to the female mastermind. Before he yields, he asks for the German word for 'suicide' and learns it; he snaps his fingers, triggering Socks to attack. Socks bites the mastermind's throat as two other German Shepherds join the fray, and the mastermind shoots one of the dogs.

In the aftermath, Jake is married to Mia and walks with Socks, who has lost one of her right front legs but remains part of their family. They have built a loving life together, with Socks recovering from trauma and finding happiness again.