East Berlin, 1963. In the middle of the Cold War, Napoleon Solo, agent of the U.N.C.L.E. (United Network Command for Law Enforcement), succeeded in bringing to the West, the daughter of a mysteriously disappeared German researcher. While he believes his mission is over, Solo is rather surprised to be twinned with a member of the KGB, to interrupt the activities of an international criminal organization that threatens the world order. The latter, under a seemingly legal commercial façade, uses the German scientist against his will to produce nuclear weapons. Constrained to put their differences aside, at least for a while, the two spies helped by an English agent try to infiltrate the secret structure.