When a team of elite operatives are killed in an ambush during a raid on a druglord's house, the focus shifts to the TRPs (Tactical Role Players) who were used to help train the operatives. The NCIS LA team is called in to investigate and find the mole in the TRP group, but in order do that, they must go undercover as a group of operatives training for a mission themselves. The team is sent to a 'kill house', which is a large complex used for training, and they are quickly overrun by the more experienced TRPs. During the second exercise, a TRP is killed, which tells the LA team that the mole is trying to cover his tracks. As they fight their way through the grueling exercises and try to piece together the clues, the team gradually narrows their focus onto Marc Inman, the leader of the TRP group. Before the team can arrest him, however, he takes Nell hostage and brings her back to another killhouse. Using everything they've learned about tactical assault, the team storms the killhouse, takes out the rogue TRPs, arrests the drug lord, kills Inman, and saves Nell.