Larrick served as a special operative in Vietnam in the 1970s, and later became a Naval officer teaching at the Naval Academy in Annapolis, MD. Claudia believes he is the only informant of Emmett and Leanne’s capable of murdering them and their daughter.
Larrick appears as a strong, principled Navy veteran, and shows open disdain for the Soviets. In March 1982, Elizabeth and Philip make contact with him under the guise of being CIA security, using Larrick's Navy file obtained from Seaman Brad Mullin. He denies killing the Connors, although he states he intended to, and had been tracking them.
Known intelligence that Larrick passed to the KGB includes:
- Reconnaissance reports on Central America.
- Communication codes for multiple on-ship systems.
- Security protocols at naval bases including Little Creek, Groton, Patuxant River.
- The location of, and access codes to, the Martial Eagle training camp.
Larrick was heavily involved in the Navy SEAL’s covert actions in Central America, specifically the Martial Eagle operation. A senior instructor for the program, Larrick provides the Jennings with access into the camp, where Contra field commanders are training on US soil.
Larrick kills Sandinista fighter Lucia after overpowering her in her failed attempt to torture and kill him. Guilty over his betrayal of his country, and angry at his fellows Seals' deaths in the Martial Eagle camp disaster, leads Larrick to turning on the KGB. He traces a clandestine KGB call center operated by George, killing him and using the switchboard to find Kate, who meets a similar fate. In his attempt to capture Elizabeth and Philip, he kills Jared Connors, before being fatally shot by Philip.