U.N.C.L.E. ends up involved with foreign affairs when the Mob takes over a small European country. Napoleon and Illya must bring back Princess Vicky to remove the mobsters, but her brother is too far in debt to protect her.

Professor Lillian Stemmler is secretly a Thrush agent, and has developed two formulas. One heightens the senses, the other reduces mental function. Thrush plans to use both to steal military secrets from a U.S. base.