CIA Agent Coen comes warn Five-0 that a rogue CIA operative was found dead in Mexico with a bullet matching Doris' service issued weapon. Steve must go to Mexico alone to find his mother and kill Sinaloa cartel leader Carmen Lucia, whom she befriended undercover or turned to as CIA suspects. Despite his promise to wait for instructions, after two months Junior goes to Mexico, tracing Steve using satellite and security cameras to assist him. After infiltrating a drug cartel storage facility, Steve and Junior find Doris, but before he can talk her into coming with them, Steve is shot and Doris is fatally stabbed by the cartel leader, whom Doris had set up successfully on deep-cover mission for the U.S. government.
—KGF Vissers