Rivera is assigned by his government to be a liaison with American law enforcement agencies on a special anti-drug project of forming a Mexican-American task force to strike against the drug cartels, notably against Reynosa. Secretly, Rivera's objective is to have revenge for his father's death by using Abby Sciuto's forensic skills to investigate the cold case while training a class of task force forensic specialists in Mexico. It is later revealed that Gibbs killed Hernandez and Rivera was counting on Abby's report to bring Gibbs down but it never reaches Mexico having been intercepted by Margaret Allison Hart, who is working on the task force project. However, Alejandro makes one huge mistake when he arrives at NCIS and later threatens Abby, prompting the entire team, including Leon Vance, to have him removed. He is duped into thinking that his sister, Paloma, had been killed, and goes to the safe house she was at, thinking that he can kill Gibbs and his father. However, he ends up killing Paloma and is then arrested for her death. He reappears in season 11's finale "Honor Thy Father" when it is revealed that he used his cartel to fund operations for the Brotherhood of Doubt after Parsa's death, as a result of the two sharing a common enemy— Agent Gibbs. Michael Rivkin (Merik Tadros) first appears in the episode "Last Man Standing" as a Mossad officer. He is working with Ziva David when she is on an undercover mission for the Mossad in Morocco (Ziva having been dismissed from NCIS in the previous episode). Later on in the episode, he is seen in the office of the head of Mossad, Eli David, Ziva's father, as Ziva talks on the phone to Gibbs. Tony becomes suspicious of the man that Ziva appears to be dating, and keeps trying to find out who he is. For example, in the episode "Legend (Part 1)", Tony asks Abby to check the records on Rivkin. In the episode "Legend (Part 2)", Michael appears as an undercover Mossad agent who is investigating the same terrorists that NCIS is investigating, killing them off one by one before NCIS can apprehend them. He is asked to leave the U.S. by NCIS agent in charge in Los Angeles, Lara Macy and later by DiNozzo, both of them citing laws that prohibit foreign intelligence operatives from working in the United States. In the episode "Semper Fidelis", what appears to be an open and shut case of an Immigrations, Customs and Enforcement agent killed by a terrorist is complicated by the presence of Rivkin, who is still in the US visiting Ziva.