British playboy Lord Brett Sinclair and his American counterpart Danny Wilde are summoned by retired Judge Fulton to an hotel on the French Riviera where they get into a fight. As an alternative to being arrested the judge 'persuades' them to work for him to apprehend criminals seemingly beyond the law. Their first assignment involves locating Maria Lorenzo - a girl identified by an unusual birthmark. Her brother, head of a crime syndicate, was supposedly killed two years earlier but is very much alive and still carrying on his illegal activities, unknown to Maria. ...
Judge Fulton sends Brett and Danny to the aid of Jenny Lindley, whose supposedly long dead brother Mark has suddenly reappeared to wrest possession of the family estate from her. The judge believes that Mark is an impostor and his suspicions seem considerable when somebody tries to kill Jenny. Whilst Mark has an alibi, a hit-man has been involved, who, in turn, is shot dead. The Persuaders find a diary, belonging to a former employee of the Lindley family, which provides the answer to the mystery but by this time Jenny has gone to see Mark and Brett and Danny fear ...
Julie Blake is murdered and, helped by her friend and fellow dancer Pekoe, the Persuaders conclude it is because she discovered that millionaire Lanny Koestler was a fake. In fact he is an actor, Morgan Alcott, employed by Koestler's duplicitous wife, to impersonate him until she can transfer his assets into her own accounts. When she has done so he will have outlived his purpose and will be murdered. The Persuaders seek to prevent this and to expose her and her accomplices.
While driving along a country road, Danny's attention is attracted by a leggy girl in a short skirt. He quickly leaves her however when he hears a suspicious sound from within the woodland, confirmed by finding a dead body. But by the time he has dragged Brett back to see it, the body has mysteriously vanished and the pair are marched off as trespassers by a hostile gamekeeper.
Knocked unconscious after a staged road block, Brett awakes in a fake hospital, from which he eventually escapes, to be told by Danny that he has a double who has been impersonating him. Reclusive millionaire Sam Milford is due in town and Brett is one of the few people he trusts to come near him. Danny reasons that the double is out to kill Sam but then realises that there is no double and Brett himself was programmed to kill whilst in hospital.
Following coincidental events in a Brighton casino, Danny is mistaken for a Soviet spy and given a mysterious list of names. British intelligence is far from happy as they were on the verge of discovering the identity of the true spy. Brett joins Danny in his efforts to locate the real Russian agent by using the list - which, rather oddly, consists of the names of railway stations.
Danny becomes the target of assassination attempts after accidentally exposing Count Marceau as a Nazi. At the same time Suzy Denton is anxious to clear the name of her late father who, thanks to Marceau, died with the stigma of being, erroneously, termed a Nazi. The key to Suzy's mission lies in the statuette of a bird which the Persuaders must obtain from Marceau along with the kidnapped Suzy.
Angie is an old male friend of Danny's from the days before he struck it rich and Danny finds it hard to believe that Angie, re-encountered on the French Riviera, is now a hitman paid to rub out a witness against corruption in big business. Despite Brett's warnings of caution Danny is prepared to champion Angie but this leads to a showdown between the two old friends, which only one can survive.
Danny finds himself in a deadly situation when a dying parachutist chains him to an attaché case, containing secret information which the British government are anxious to obtain. Not only does the head of MI6 mistake him for a renegade C.I.A, agent but X-rays of the case show that it contains an electronic device which will cause it to explode unless unlocked with a key. Brett tries to locate the key whilst Danny evades 'Franz Schubert', an unfriendly European also after the attaché case.
Thaddeus Krane is a ruthless millionaire who has made his wealth from the sufferings of others and his young secretary Cliff aims to expose him by contacting Brett. However Cliff is killed and Brett abducted and whisked away so that Krane's henchmen can ascertain how much he knows. To confuse Krane Judge Fulton persuades Danny to impersonate Brett, and all is going well until a lady friend of Brett's almost ruins the situation with her curiosity.
On holiday in Scotland the Persuaders find a crashed plane containing dead scientist Brian Wilks and a formula he has written down. Three girls turn up claiming to be the dead man's daughter and after the formula, a way to make cheap, synthetic fuel, but the Persuaders correctly Carla as the true claimant. Further complications arise when both Andreas Theopolos, the dead man's business partner, and tycoon Sir Hugo Chalmers both lay claim to the formula - which one of them, having already murdered Wilks, will kill to obtain.
Somebody in British intelligence is selling secrets to foreign powers and Brett agrees to pose as the traitor, incurring the curiosity of British agent Kay Hunter, who follows him. Brett is approached by a man named Krilov, anxious to buy secrets from him but when it is discovered that Brett is a decoy, Krilov imprisons him. He is rescued by Danny and Archie, a foolish, impecunious relative of the Sinclairs, and manages to flush out the real traitor. However Krilov abducts Kay and it is down to Archie to save the day.
Danny is mistaken for Lomax, an international criminal, and taken to meet Mitchell, who has engaged Lomax to master-mind a plot to rob an American air force base of a huge amount of gold bullion. Learning of his friend's plight, Brett poses as the gang's getaway pilot but the game seems to be up when the real Lomax arrives. Can the Persuaders rely on female gang member Charlie to save them?
When Danny buys a ramshackle country cottage which he plans to renovate he is surprised by the fact that local squire Rupert Hathaway is desperate to buy it from him and will resort to violence when Danny refuses to sell. A woman called Lucy comes to see Danny. She is a member of the Fraud Squad, investigating the death of a colleague whom she believes was killed by Hathaway. The squire is at the centre of some highly illegal goings-on to which the cottage is crucial and Lucy seeks Danny's help in bringing him to justice.
Brett wakes up to a unique 'morning after'. He has acquired a wife, Kristen, and there is evidence that a legal marriage took place. However, one of the two witnesses is involved in a plot to abduct Swedish diplomat Lars Seelman, arriving in Britain on important business. Will Kristen aid the plotters or will her attachment to her new husband lead her to help him save Seelman?
After Brett enters his car for a motor race, attempts are made on his life. A man called Vine approaches him, asking him to throw the race. He is working for Louise Cornell, head of a race fixing gang but she denies any allegations of trying to kill him - she just bribes people to lose. Could the would-be assassin be Jenkins, a former racer who, after an incident years earlier where he tried to overtake Brett, leading to an accident which incapacitated him, was never able to drive again?