Steed's colleague Sean Mortimer comes to see him in a very confused state. He knows there is a traitor in the organization but he has been drugged to put him in an amnesiac state and he can remember little else. Mrs. Peel investigates but she too falls prey to the drug as she and Sean are abducted by bikers. It is down to trainee agent 69, Tara King, to whom Steed is introduced by spymaster 'Mother' to help him save the day. Finally Miss King becomes his new partner as Mrs. Peel's missing husband reappears and she goes off to join him.
Secrets are leaking out of Cipher HQ like a sieve, but all of the employees insist that everything has been "perfectly normal." However, The Avengers find a link between the stolen information and a window cleaning service.
The Avengers investigate the Anastasia Nursing Academy, whose matron and her partner Glover are developing the ultimate in germ warfare - a virus which causes the victim to literally sneeze themself to death. Their aim is to sell it to the highest bidder and it is the task of Steed and Miss King to protect the doctors who can provide the antidote.
George is the country's top computer but somebody is attempting to sabotage him via shooting, acid corrosion and shutting him down. He is able to send part of a message on a print-out but the Avengers are still none the wiser as to who is trying to disable him and call upon his creator for clues.
Somebody is leaking secrets from the Carmadoc research institute and suspicion falls upon Steed, who has been spending some time there. He is accordingly put under rather luxurious house arrest at Mother's, whilst Miss King and her somewhat incompetent new partner Watney unmask the real traitor.
Steed comes into possession of a jewelled ornamental dagger, known as the Falcon. It is highly sought after because it will lead to the whereabouts of the world's most valuable black pearl. Unfortunately, everyone who has ever owned the dagger has met an untimely end. Steed and Miss King must find the pearl and break the sequence.
Having broken his leg, Steed is now convalescing in a private hospital, where he is visited by Miss King. However, she has been followed - by Gerald Kafka - the driven former head of Murder international. Thanks to Steed he was caught and sent to prison for seven years. Now he is released and swearing vengeance on the man who put him inside. His plan is that Steed will die at exactly twelve noon. With Steed incapacitated, it is down to Miss King to save the day.
Directors of the Capitol Land and Development Company are being killed. They have the tender for the Cupid project, an underground government headquarters in the event of a nuclear war. Clues such as a red nose and a giant footprint lead the Avengers to a home for retired clowns, irate that the project will flatten a sainted variety theatre and with an agenda of their own.
When three thousand army rifles are stolen Steed suspects the visiting Colonel Nsonga, who is planning a revolution in his home country in Africa. Actually a mercenary woman called Adriana has the guns, which she auctions off to the highest bidder. This turns out to be Nsonga and the chase leads to the grounds of Adriana's house where the arms are stored and due to be tested on a human target - Miss King!
Enemy agent Arcos has invented a form of instant plastic surgery and he uses it to imprison Steed and create a double, who is sent to throw a spanner in the works at an important peace conference at a country house. Although Steed overpowers his jailer and escapes, Miss King still has to deal with the matter of more than one doppelganger for her colleague though none seem to survive for very long. Until Steed arrives she is assisted by a dashing blond German count.
Members of the Institue of Timber Technology have been killed to prevent them from standing in the way of a dastardly plot hatched by WormDoom Ltd, a pair of assassins who have perfected a chemical which destroys all kinds of wood and which they plan to release from pillar boxes around the country... unless Steed and Miss King can stop them.
Following up a clue found on a dead agent Steed and Miss King pose as a married couple ,enabling them to infiltrate the Alpha Academy, where they claim they wish to enrol their 'son'. The academy is run by Brigadier Brett and is supposedly for youngsters who possess super-intelligence but it is in reality a training ground for a force who seek not global but extra-terrestrial domination.
A succession of British agents have been killed in different ways but each one has been carefully wrapped in polythene before being dumped in a graveyard. With Miss King on her holidays Steed is joined by Lady Diana Forbes- Blakeney to investigate a sinister factory which houses the deadly computer REMAK - Remote Electro- Matic Agent Killer, which must be destroyed.
Having been rendered unconscious by knock-out gas in his pursuit of rogue agent Jimmy Merlin, Steed awakes to find that London is deserted and under martial law, headed by Brigadier Hansing. Under cover of a supposed evacuation, the Brigadier, incensed that he is to be retired from the army, has planted an atom bomb to destroy the capital. All Steed has to do is find it.
With Miss King out of action nursing a broken ankle Steed goes it alone when Scotland Yard colleague Sir Arthur Doyle brings him in on a murder enquiry, with an abundance of clues, each one pointing to an illustrious suspect. In fact bogus cops Earle and Gardiner are operating a racket whereby they deliberately incriminate worthies as murder suspects and then blackmail them. Their latest target is Steed and his supposed victim is Miss King.
With whole weeks missing from his life and evidence of actions that he simply cannot remember, Steed finds himself in an endless series of 'deja vu' situations. In reality he is slowly being hypnotised and the aim is to mesmerise him into killing 'Mother'.
To celebrate his birthday 'Mother' goes to visit two elderly aunts to whom he tells a story from the Avengers' case files. It involves a criminal caper to steal art treasures. The treasures were to be held for safe keeping in an underground vault in the event of a national emergency but the criminals aimed to squirrel them away once in the vault. It is a hair colour changing story indeed.
The vicar of a Norman church asks the Avengers' help when a team of archaeologists excavating a site underneath the church are all killed and their bodies rendered completely devoid of any energy. This is due to a little black box which sends out deadly charges of electricity. Furthermore its charges are nurturing a race of thingumajigs, pure energy creatures which will eat anything and must be stopped before they do great harm.
Following a tip-off Steed and Miss King are present when a member of the Acme Precision Combine is stabbed, seemingly by a sleep-walker who has no recollection of the murder. This leads the Avengers to a clinic run by Dr. A. Jaeger who may or may not be programming deadly sleep-walkers.
Coming home from a costume party Miranda Loxton witnessed a killing by a member of Murder International and Steed is assigned to protect her until she gives evidence at the trial. Only Miss King knows that he has taken her to a boyhood haunt but then she is caught and wakes up in a sinister hospital where she is pumped for information about Miranda's hideaway.
Three men and a woman called Circe politely call on the country home of Steed's friends, married couple Bill and Laura Bassett. Unfortunately their visit turns sinister as they plan to implant explosives into the throats of the couple and send them off to destroy a nearby peace conference. Happily for the Bassetts - and the conference - Steed is coming to visit for the weekend, and he knows what to do.
Miss King is abducted whilst visiting an antique shop and wakes up in a room beautifully furnished in a style from fifty years earlier. She is addressed as Pandora. Steed follows a lead which takes him to retired World War One agent Lasindell, the love of whose life was called Pandora and bore a strong resemblance to Miss King. It is a plot by his greedy relations to make him divulge the location of his fortune or else Pandora, alias Miss King, comes to harm.
Three captured Russian spies are being held at the seemingly escape-proof Oldhill Monastery, but two of them do manage to escape, simply by making themselves seem invisible, thanks to the contents of a bottle of Lizard vodka. They both succeed in eliminating their chosen victim. The third one is about to make his getaway. And his mark is Steed.
Found wandering in a snowy field Helen Pritchard claims to have seen a man who was supposed to have been a corpse but was very much alive. This leads Steed to investigate the Happy Meadows funeral parlour and the cheery Mr. Bagpipes Happychap. Unfortunately the undertakers seem unable to keep their 'stiffs' from walking and Steed has to arrange his own funeral in order to find out more, though ultimately he and Miss King do get a send-off that is out of this world!