U.N.C.L.E. and Thrush agents compete to gain possession of a mind-reading device created by a magician who has been murdered by Thrush.

When secret ""File 40"" documents turn up outside headquarters, Waverly assigns Solo and Illya to find out if George Donnell is a double agent. Carla Drosten is too anxious to accuse Donnell and Solo must use special ""Waverly rings"" to try and expose the real double agent.

THRUSH agent Elom tries to kidnap a geologist who has developed an earthquake activating machine, but mistakes debt-ridden salesman Buzz Conway for the scientist. Solo and Illya let THRUSH go on thinking Conway is the scientist, while Elom lets his attraction for THRUSH agent Narcissus Darling interfere with his judgment. Conway is captured, and Solo and Illya must rescue him and find the machine.

Solo and Illya board the Adriatic Express train on New Year's Eve to intercept Madame Nemirovitch, a THRUSH agent who is carrying a chemical that is capable of stopping the reproductive process. Eva, a young girl who delivers a message to Madame Nemirovitch as the train leaves, is caught on board. Throughout the evening, the THRUSH agent and Solo and Illya engage in a battle of wits as the train speeds along its route.

Solo and Illya try to protect Professor Lillian Stemmler from THRUSH after she invents a drug called Plus X, which heightens all the human senses. Unbeknownst to them, she is a THRUSH agent herself who at first cooperates willingly, then has second thoughts. But THRUSH agent Rollo kidnaps her daughter Leslie and forces her to cooperate. The drug is given to three THRUSH agents who will attack a U.S. government plutonium plant using their superior senses, while at the same time the guards will be given a dose of Minus X, which dulls the senses.

A top-level U.N.C.L.E. conference is to be held in Switzerland, but a nearby boys' school is actually a THRUSH front run by Mother Fear and Dennis Jenks that is training its students to be assassins. Solo is captured by the boys, and, when he refuses to reveal the conference location, is forced to operate the controls of two electric trains so they do not collide with each carrying a vial of deadly nerve gas. Illya and Anna Paola, a social worker who resent children, are also captured. The escape, and arrive at the conference just as the boy's choir is ready to kill Waverly and the others with THRUSH rifles from under their robes.

The 'Re-collectors' claim to be trying to locate works of art stolen by the Nazi's but all is not as it appears.

THRUSH eastern in Japan acquires a volcano-activating device, and Solo and Illya, along with Cricket Okasada, a film student, infiltrate a toy store and a karate school to find it. THRUSH leader Mr. Kutuzov oversees local THRUSH head Harada in the operation, and Solo finds himself fighting for his life against a life size sword wielding puppet.

Illya Kuryakin infiltrates a South American prison camp where Thrush are storing the 'Ultimate Computer'.

Illya investigates the mysterious disappearance of cats in Soho, and he and Solo discover that a salon run by Madame De Sala is a front for her plan to develop a rejuvenation process, which De Sala plans to use on the now elderly target of her romantic desires, Sir Norman Swickert. Assisted by Joanna Sweet, a nurse, they end up in the bottom of a wine press. Meanwhile, THRUSH agent Jordin plots to obtain the process for THRUSH.

While investigating a THRUSH plot to sabotage space shots, Solo and Illya are incapacitated by a quartzite radiation projector. Waverly assigns new trainee April Dancer along with over the age of retirement agent Mark Slateto find the antidote and destroy the plan. April infiltrates the cosmetics company of THRUSH agent Arthur Caresse as a model, but she is uncovered by Caresse's sister Jean.

Alexander (Rip Torn) a megalomaniac industrialist, plans to conquer the world like his namesake, Alexander the Great by breaking each of the ten commandments along the way. he has his henchman Parvix (David Sheiner) steal the army's ""will gas"" to help him do so, and Solo investigates. Solo encounters Tracey Alexander (Dorothy Provine), Alexander's ex-wife, who wants to tag along with Solo to get the money Alexander owes her. The trail leads Solo, Illya, and Tracey to a posh party at Alexander's, where Solo defeats him in a human chess game; to a tomb, where Alexander and his aide Dr. Kavon (David Opatoshu) leave Solo tied under a descending scimitar while Illya and Tracey are hanging over a bottomless pit with a candle burning their rope; To Alexander's farm in Virginia, where Illya is nearly cut in two by various farm implements.

Napoleon Solo is given the job of searching for Thrush security records.

Illya goes to find Thrush's vaporizing machine, but is captured by Sophie, the headstrong daughter of the local tribal chief, Sulador. in New York Solo convinces retiring THRUSH agent David Lewin that THRUSH intends to kill him, and elicits his help. Lewin and Solo are taken to the base in the desert, just as Illya leads the band of nomads, whose confidence he has gained, in an attack on the base.

French fanatic Robespierre seeks to destroy France's vineyards in his quest for virtue, and Solo enlists the aid of scientist Raoul Dubois and his daughter Albert in combating the plan. Illya is captured by THRUSH agent Carl Voegler and, with a target painted on his back, is hunted through the woods by Voegler's archers.

THRUSH has developed with the aid of Dr. Elias Swan, a strain of minute, deadly bees. THRUSH agent Mr. Mozart captures Illya and Tavia Sandor and uses a high-frequency sound machine that threatens to shatter their eardrums to force Illya to take him to U.N.C.L.E. headquarters so he can release the bees. Illya does so, but Mozart is intercepted, and in a battle on a rooftop Mozart is shot and the bees get loose.

Solo and Illya discover that the world diamond market is being affected by a gang of English criminals headed by Blodgett, who smuggle diamonds inside pudding sold unwittingly by Victoria Poque. They enlist the aid of a master diamond thief, Rafael Delgado. Solo and Victoria end up in Brazil, with Solo tied to the front of a cannon and about to be executed.

Alexander (Rip Torn) a megalomaniac industrialist, plans to conquer the world like his namesake, Alexander the Great by breaking each of the ten commandments along the way. he has his henchman Parvix (David Sheiner) steal the army's ""will gas"" to help him do so, and Solo investigates. Solo encounters Tracey Alexander (Dorothy Provine), Alexander's ex-wife, who wants to tag along with Solo to get the money Alexander owes her. The trail leads Solo, Illya, and Tracey to a posh party at Alexander's, where Solo defeats him in a human chess game; to a tomb, where Alexander and his aide Dr. Kavon (David Opatoshu) leave Solo tied under a descending scimitar while Illya and Tracey are hanging over a bottomless pit with a candle burning their rope; To Alexander's farm in Virginia, where Illya is nearly cut in two by various farm implements.

Illya investigates the mysterious disappearance of cats in Soho, and he and Solo discover that a salon run by Madame De Sala is a front for her plan to develop a rejuvenation process, which De Sala plans to use on the now elderly target of her romantic desires, Sir Norman Swickert. Assisted by Joanna Sweet, a nurse, they end up in the bottom of a wine press. Meanwhile, THRUSH agent Jordin plots to obtain the process for THRUSH.

Solo uses hillbilly clairvoyant Clemency McGill to counter the efforts of Count Zark, a vampirish THRUSH agent who plans to use radioactive bats to jam the world's radar systems from his castle. Solo and Clemency make their way to the castle with Illya, but Zark manages to release the bats.

THRUSH agent Harry Pendleton is captured and commits ""suicide"" with a reversible chemical, but his superior, Simon Baldinado, refuses to revive him because he is attracted to Pendleton's girlfriend, Jojo Tyler, Solo gets Jojo to help U.N.C.L.E. retrieve the ion projection machine Baldinado has hidden at the mortuary front for THRUSH by feigning affection for Baldinado, who allows his personal plans for Jojo to affect his judgment.

Solo and Illya travel to Circe to intercept a drone plane carrying a load of THRUSH cash. There, they encounter THRUSH agent Colonel Hubris, as well as two local girls who are looking for husbands.

THRUSH is so eager to get their hands on a boy genius that they murder the boy's father. But then they have to deal with the boy's madcap aunt.

Squire G. Emory Partridge returns, having acquired in Alaska a large quantity of Quadrillenium X, a very heavy metal with high magnetic powers which THRUSH wants to use to disrupt world communications. Solo and Illya are nearly killed by the local Eskimos, but are saved by the chief's daughter, Murphy. Partridge and his niece Victoria capture them, but they escape only to end up in a tavern brawl.

Solo, while searching for a secret map in Nevada, swallows an amnesia capsule just before being captured. THRUSH agents Arum Tertunian and Longolius try to revive his memory with a seductive female agent, Mara, while Illya races to find him before he starts to remember.