Final Payment is a Cold War thriller. When an Israeli aircraft struck by a missile fired from Egypt crash lands in the occupied Sinai, CIA officers Serina Gray and Clay Kinkaide are tasked to purchase the damaged Soviet weapon. The Israeli Mossad agrees to sell it, but demands a strange price: $10 million cash and Joachim Van Altmann, a U.S. Citizen serving as caretaker officer on a ship marooned in the Great Bitter Lake, whom they assert is a Nazi war criminal. Van Altmann is not a Nazi, but an NSA officer operating a secret monitoring station on his ship. When the Mossad rejects CIA assurances about him and threaten to kidnap or kill him if the exchange is not made, Clay and Serina place Van Altmann in Israeli custody as security for their pledge to help locate the real Martin Bormann. A world-wide search for Bormann locates him in Paraguay and he is captured in a black operation by an American-Israeli team, but one Israeli is wounded in the assault and the other appears to be the cause. Bormann manages to thwart the team's escape and they are forced into hiding in Argentina. During the evacuation of the Israelis, Serina is ambushed by the police and Clay, who witnesses her capture, can do nothing to help her. She is brutally tortured, but remains silent to protect him. Clay determines to rescue Serina, whom he has fallen in love with, and with help from Tomaz, a local agent, goes in search of her. He is wounded while attacking the police installation where she is held, but is still able to escape with her. They find refuge and medical help at a lakeside resort and escape from Paraguay after a perilous boat passage down the Parana River. Back in Tel Aviv, Serina and Clay learn they must outwit the Soviet double agent who betrayed them in Paraguay, obtain the missile and gain Van Altmann's release, all while blocking a Soviet plot to cause an atomic detonation in Israel.