Gibbs has been rejecting every agent sent to replace Tony, so Quinn, the agent who trained them shows up and asks Gibbs what he's looking for, Gibbs tells her to stay and observe his team so that she could get an idea. They then get a call about a Commander's car blowing up. The Commander was killed, his wife was injured. Abby checks the car and says the car was tampered with. The wife is a JAG lawyer so they try to find out if anyone she prosecuted went after her. They talk to JAG and learn she took some time off for personal reasons, which contradicts what the daughter said that she was working on a case. They learn she went to Argentina. They learn she went to look for her brother who's an NCIS agent who's been undercover. They learn the agent stopped making contact for nearly a year and there was a rumor he's dead. But the sister hired an investigator who found him, which is why she went. Now they're concerned did he go rogue or turned. When he shows up, someone tries to take him out but he takes care of them. Gibbs shows up and asks him what happened. He said he was approached by a man who wants him to work for his family. And the family is engaged in some illegal practices. And to solidify his position he got involved with man's sister. Later after his sister went looking for him, they learned who he is and tried to kill him but he again got the better of the one sent to kill him and tried to warn his sister cause he knows they will go after her. But he was too late. He wants to go after the man and his father and fortunately for him, they're in the US, so they try to get them. But the guy is ready to do anything to get them.