When the beautiful woman who stole a priceless Faberge bauble from his shop is identified as a Pameranian courier, Mannering decides to visit the country's embassy and demand satisfaction. He is intercepted by British intelligence agents who convince him to go behind the Iron Curtain and break up the ring of art thieves who have been hiding behind diplomatic immunity, using his real occupation as an antiques dealer as his cover.
Having attended the funeral of his old Army buddy,Jim Carey,Mannering is surprised to learn that the man is far from dead and the funeral was but a smoke screen. Carey is planning to steal a priceless jewel from a museum and wants the cooperation of Mannering,initially as a fence,later as a gang member and,to ensure his cooperation, Carey takes Cordelia hostage.
John Mannering does a deal with a crooked insurance agent in order to recover an Aztec mask worth a hundred thousand pounds from an ex-convict,Mark Seldon. However, Seldon's old gang boss wants the mask for himself and threatens Seldon's daughter Anne as his security. Mannering now has to recover the mask by saving Anne.
Mannering agrees to travel to a country racked by civil war to transport a valuable statuette back to London. The rebel leaders hope that the art object will bring them money to buy arms and ammunition to overthrow the tyrannical government. During his flight from the country, Mannering is dogged by the secret police who seem to know his every move even before he makes it.
Mannering and Cordelia are in an Iron Curtain country where they are about to hand over some money at a secret rendezvous. However Mannering's contact has been caught by the police and forced to name his contact. Though warned to keep away Mannering and Cordelia fall into a trap and she is taken by the police. Mannering plans to spring her by taking his own prisoner - the chief of police.
A gang led by Morgan Travis is planning to steal the Crown Jewels and also to kill Mannering,replacing him with 'Eddie',a man who has undergone plastic surgery in order to become the Baron's exact double.In fact the gang kill Eddie by mistake but are unaware that Mannering is still alive. Mannering must now impersonate Eddie impersonating himself and convince Cordelia into the bargain.
Having convinced Cordelia what is going on,Mannering goes to London with Morgan Travis's gang to get to the Tower of London. Unfortunately,whilst the Baron is doing his best to copy Eddie's mannerisms,a close friend of the deceased recognizes that he is not Eddie. The gang now force Mannering to assist them in their robbery of the Crown Jewels.
Mannering's assistant,David Marlowe,is abducted from the shop and a ransom demanded for his return. Specifically the ransom money is to be obtained by Mannering selling a fake Renoir painting to art collector Sir Richard Ellacott. On Templeton-Green's authority Mannering sells the painting and obtains the money,which is to be delivered to Sir Richard's nephew,Roddy. Mannering knows that Roddy is one of the kidnappers but must be careful not to put David's life at risk.
Whilst in Switzerland Mannering and Cordelia meet Peter Franklin, an American undercover agent and an old flame of Cordelia. He has stolen a strain of a deadly germ warfare virus from the laboratory where he was secretly working. When he is killed and the virus goes missing, Mannering intends to get to it before Dr. Ingar Sorensen, who developed it and the unscrupulous free agent Holmes.
Mannering is asked to handle the sale of "The Legions of Ammak", a golden necklace that contains seven perfectly matched black pearls from a Middle Eastern king to an eccentric millionaire. Mannering vouches for the authenticity of the necklace, but his assistant, David Marlowe notices that the king wore the wrong school tie at the ceremony. Mannering discovers that an actor, pretending to be the monarch sold the jewelry, and the purchaser, a man not known for purchasing art, has interests in region oil fields and fears that he has been duped into aiding a palace coup.
Asano, an aging Japanese man, agrees to sell a family heirloom, a 500-year-old samurai sword, to Mannering for 10,000 pounds. When Asano delivers the sword to the antiques dealer, he bumps into Sterling, an British army officer who suffered the Japanese POW camp commanded by Asano. Sterling plans on exacting revenge for his treatment at the hands of the Japanese soldier and when Asano is found dead, Mannering must project Sterling from Asano's vengeful servant.
Mannering stops his car to pick up damsel in distress Jill Prentice but he is shot at and crashes the car. When he comes to Jill has gone and he finds himself having weird flashbacks involving a man with a gun. D.I. Walsh believes it is just concussion but Mannering has to piece together the maze in his mind and reach Jill before the gunman can stop him.
Louisa Trenton is an old friend of Mannering and she is clearly in financial trouble because she offers to sell him some miniatures which are very valuable and have long been in her family. Later she rings the Baron,who goes to meet her at a discotheque,but finds that she is dead. The police believe that she killed herself but Mannering is certain that she was being blackmailed - and that the blackmailer murdered her. He has several suspects to choose from.
Having received a tip-off that the Lynstead art collection is about to be burgled Mannering lies in wait with the police for the thieves but one of the officers is shot and killed by gang leader Greg Wilde,who subsequently is charged with murder and sent for trial. As the only surviving witness to the killing, Mannering is in a vulnerable position when Wilde escapes from custody and comes after him with murderous intent.
While searching for a missing crate of valuable antiques, Cordelia discovers the murder and is promptly abducted by the killer. Mannering tracks her to the freighter and stows away in an effort to rescue her. On board, he stumbles across an undercover CIA operative who suspects the ship's crew is engaged in espionage activities for a foreign power.
While being held on a blacklisted freighter, Mannering and Cordelia discover that the ship's crew is part of a plot to knock an American space capsule out of orbit, retrieve the spacecraft and deliver it to an unfriendly power. Mannering manages to radio the U.S. Navy and escape in a lifeboat to a nearby island, where he tries to locate the command station before the search parties can locate him.
The Vitale family are in possession of an emerald cameo brooch,which is said to be cursed and brings death to its wearer. Cristina Vitale arranges to sell it to Cordelia but she is killed before the transaction can be completed. Soon afterwards,her father is also slain. As the new owner of the brooch Cordelia is now in danger but is the curse genuine or a cover for something equally as sinister?
Nikki Holz sets out from Germany to London with important information for Mannering but she is abducted before she can meet up with him. Mannering and Cordelia learn that her captors are members of a neo-Nazi organization who are selling off art treasures in order to fund their attempts to gain dominance in Europe, a discovery which leads the Baron into a dangerous climbing adventure.
The Petrograd icons have been stolen but Mannering tracks them down and is about to put them into a safe deposit box when he is knocked unconscious and,on coming to,finds that they have been stolen again. His investigations lead him to the urbane Jim Gaynor and the Peerage gentlemen's club,where Mannering engages in a game of poker - the stakes being the further recovery of the icons.
Delivering a consignment of Medicis to a wealthy female client,Mannering discovers the door open,the lady missing and a strange man inside. Investigations reveal that she had been giving money to a bizarre religious sect with which she had recently been involved,whose leader styles himself the Chosen One. When Mannering decides to look into the sect he finds that he has become the one they have chosen to be killed.
Mannering is approached by a glamorous French widow,Madame Devereaux,who sells him an expensive necklace,the seven eyes of night. after she has gone,however,he realizes that she is an impostor and a member of a gang duping buyers into believing they have bought something valuable. He hopes to get to the gang by following secretary Nancy Cummings.
Mannering has sold some antiques on behalf of Madame Nicharos, the wife of a deposed Balkan president. Before he can deliver the money to her he is confronted by the general who led the coup. The general seeks both the money and Madame Nicharos in order to strengthen his hold on power.
It would appear that the Mona Lisa has been stolen from the Louvre. But is it the actual Da Vinci painting or a forgery substituted to thwart the thieves? One of the robbers flies into London secretly and arranges to meet with Mannering so that he can authenticate the spoils whilst a French spy bugs the Baron's phone so that he too can find out further details. Ultimately Mannering finds himself the prospective saviour of one of the world's most iconic paintings.
Cordelia travels to South America on Mannering's behalf to meet an explorer who has something to tell them. Then she disappears and Mannering travels out to find her. He discovers that she has been arrested for discovering a secret that the authorities do not want to come out into the open,involving the stock-piling of hidden weapons.
Mannering is about to give a valuation for a client when the man dies. He is a former bullion robber and he has been murdered by Ashton,his erstwhile partner in crime who is looking for the hidden loot and intends to use the dead man's daughter in order to locate it. This leads the Baron and Cordelia to an old dark house in the country where mysterious goings on have been reported.
At a party in his house gangster Mario Navini kills Pia Vallachio and,helped by his younger brother Bruno,disposes of her body in a quarry. They are observed by sole witness Maria Pullerno,who flees in terror. The Italian Minister of Justice,Vittorio Guardi, asks Mannering to obtain a witness statement from her,as a result of which the Baron and Maria end up besieged by the Navinis in the police station in the village of Santa Montena.
In Scotland Douglas MacRae,another antique dealer and friend of the Baron,is murdered by American mobsters who intercept him in the course of a 'job he has to finish'. Though the coroner's verdict is one of accidental death,Mannering is not convinced,especially when he spots one of the gangsters wearing Douglas's ring. His pursuit of the gang exposes a plan to flood the country with counterfeit money.
The Baron is to meet Stanley White, a man he has never seen before,for information about a valuable sword. However film-maker Arkin Morley is also after the sword and has Mannering abducted and imprisoned in a railway goods truck whilst Compton,one of his men, posing as Mannering, makes the contact with White. Mannering has to escape and intercept Compton before he gets to White.
An airline steward is found dead with a gold medallion in his possession - it is one of several stolen from the Vatican and links him to one of the biggest art smuggling rings in the world. To investigate it the Baron travels to Rome,meeting up with ex-girlfriend Cathy Dorne,who is being forced by her boss Nick to be part of the smuggling gang and who helps Mannering bring its members to justice.