A beaten-up Whiting shows up at Deeks' door. She had answered a text from an LAPD officer, Sean Turner, who said he was in trouble. When she got there, he was dead after being shot. She was attacked before she could call that in. An APB was put out on her in connection with Turner's murder. Kilbride reluctantly agrees to let Deeks investigate Whiting's theory that a group of rogue cops are protecting fentanyl dealers. Sam assigns an unhappy Rountree to babysit Whiting. She badgers him into going with her to check out a lead. LAPD releases video that incriminates Whiting. All the security cameras but that one have been disabled near the murder scene. Whiting tells Rountree they're staking out a corrupt narcotics detective. Turner's widow informs Sam and Deeks that he was working himself to death. His symptoms match opiate addiction. Kilbride discovers that Rountree and Whiting are chasing down a lead. Since the detective is talking to Scott Upson, a member of a fentanyl-dealing gang, he excuses Rountree for now. At her home, an armed Kensi rebuffs a man claiming to be an LAPD detective who's looking for Whiting. Whiting chases Upson then Rountree gets the drop on him. Someone sent Whiting a text two hours after Turner was killed. Upson talks about the gang's underground fights and how the gang is leaving L.A. Rountree volunteers Sam to go undercover as a fighter. Sam fights a man-mountain played by WWE superstar Sheamus. There are drug deals happening during the fight. Sam determines the fighter is gang leader Odin and Kilbride orders the raid. Everyone gets arrested and the drugs are seized. Deeks and Kensi go home to save Rosa from Roberta. Whiting and Rountree reach a detente. Kilbride talks to Sam about his regrets concerning his family.