Caroline is taken prisoner by escaped murderer Colin Grant, a man whom she helped to imprison. She is taken to Grant's hide-out where he has assembled a mock court-room, with himself as prosecutor and cardboard cut-out figures as jurors to decide if Caroline deserves to live. As the other Protectors hunt for her, she comes to see that Grant is playing out the events of the death of his mother, the cause of his insanity.
The Protectors are asked to keep a watch on the body of recently deceased robber Ralph Corder, in the hopes that the news of his death will flush out his former associates. Indeed two of them, Robard and Mason, turn up, to convince themselves that Corder is actually dead, Robard actually approaching Harry for the news. Mason is photographed with a hidden camera, entering Corder's house and both men are trailed by the Protectors to lead them to the loot.
Investigating a suspicious death in North Africa Harry is mistaken for a drug smuggler and asked to take a consignment to Malta. Here he learns that the operation is organized by Australian James Leroy Mallory, who is also running an illegal trade in blood plasma. Harry is joined by Caroline, who poses as a client in order to meet Mallory. Unfortunately he discovers who she is and the other Protectors have to come to her rescue.
Following the murders of two members of the Protectors in New York and Japan and an attempt to kill Paul, it is apparent that somebody is out to eliminate the Protectors organization. Next, Harry is abducted by the henchmen of Jason Howard, who is the man behind the killings. He is taken to a factory owned by Howard, where he is told that he will be crushed to death unless he supplies the names and locations of all members of the Protectors.
The Protectors are out to rescue Bennett, a Canadian agent in possession of American-Canadian defence plans, who has been captured by the Russian Shkoder and taken to a clinic in Paris. After faking a car accident the Protectors gain access to the clinic and locate Bennett. However they must work out if it is Bennett himself or a Russian decoy made to resemble him through the use of plastic surgery.
In a story which unfolds in reverse, Harry is alone on an unpiloted plane and we see how he got there. He was abducted by Colin Foster, who blames Harry for his brother's death. Foster flew the plane to take-off but then he parachuted out, leaving Harry, who has no pilot skills, to require Paul's on the ground assistance to talk him down.
The Protectors are involved in ling gang but it all goes wrong. The gang escapes and Paul is left temporarily blinded. The gang, aware of Harry's association with Paul, employ Vickers, another American, to impersonate him in order to get the sightless Paul to give him as much information as he can about the Protectors, in particular Caroline.
Harry is appointed as the bodyguard for a visiting Middle Eastern president but his ex-wife Laura turns up in a frantic state. The president's political opponent Kahan has had the Rule's son Johnny kidnapped and he will be harmed unless Harry shoots the president. A charade follows in which Harry appears to do as he is ordered and Caroline then kills Harry.
Harry is celebrating his birthday at Caroline's house but whilst she is out shopping, an injured fugitive turns up. He is Douglas Perston, a South American diplomat being pursued by his political rivals, who intend to kill him. In protecting him Harry also becomes the hunted so it is a good job that Caroline gave him a shotgun as a birthday present.
Club owner George Dixon asks the Protectors to guard his niece Chrissie, the key witness in a murder trial after a killing at his club. However she is less than keen to be protected and when she disappears and is linked to a bullion robbery, two of whose perpetrators are shot, her relationship with the third man is called into question.
Ditzy American tourist Linda McCall is on holiday in Malta when her pet poodle is stolen. The thieves are Felix Da Costa and his girlfriend Mary Laroche who intend to use the dog in a plan to smuggle a secret microfilm off the island. However, by the time that Linda has enlisted Harry's help in retrieving her pooch, the dog has swallowed something that makes it the centre of an island-wide dog hunt.
Unhinged by his experiences fighting in the war in Vietnam, Colonel John Hunter goes berserk at a disused air-base, killing security men whom he imagines to be the Vietcong. Whilst the police want to shoot him, his wife asks Harry, who knew him, to don an American uniform and talk him into giving himself up. However Hunter's deranged state of mind puts himself and Harry in jeopardy.
In Rome Harry and Caroline are approached to deliver a case to Prince Carpiano at his villa but its contents are such that they have to fight off two attempts to obtain it. Then they realise that it is carrying a bomb; they have been used as decoys whilst another courier takes the genuine article to the prince. In fact its contents are the funding for a proposed right wing coup devised by the prince. The Protectors must stop him.
The Protectors are approached by Laura Sutton, who is afraid that her brother Jimmy has been recruited to work for Quin, an internationally known ruthless mercenary whose only concern is money. Harry travels to Spain in search of Quin and ends up in a face to face confrontation with him.
The Protectors are in Copenhagen, where their services are required by a wealthy widow, Madame Andersen. Her young daughter Eva has been kidnapped and is being held to ransom in a disused fort. Harry agrees to act as the bagman and delivers the ransom to the abductors. However, things do not go according to plan.
In Venice there has been a daring robbery, the spoils being a priceless art collection. The Protectors learn that the robbers are a terrorist gang who aim to sell their prize to the highest bidder in order to buy armaments for their cause. Helped by the river police Harry determines to thwart the gang.
Irena Gayevska is a young Russian scientist who is anxious to defect to the West and to marry her boyfriend there. Because of her skills she is a valuable defector and the Protectors are assigned to smuggle her over the border. Inevitably her absence is detected, leading to a pursuit by the Soviet forces.
Following a jewel theft in Denmark, a con artist named Bergen is responsible for double-crossing a number of people. The swindled parties want revenge and seize Bergen's daughter, Kate, who is unaware of what has been happening and has played no part in the heist itself. The Protectors are engaged to rescue her but Caroline is also endangered.
The Protectors are hired to combat industrial espionage after it becomes apparent that somebody is leaking information from a cleaning products factory. All the necessary precautions are put into play but nevertheless information from boardroom meetings is still getting out, pointing to an employee as the culprit. Harry decides to set a trap to hoist the traitor with their own petard.
Caroline undertakes a solo assignment on behalf of wealthy Cedric Parton. His son Caspar is living in Venice and is making a number of very considerable withdrawals from his bank account, all of which are in favour of somebody called George Milworth. On the face of it it would appear that Cedric is being blackmailed by George but when Caroline arrives, there is no George to be seen and the motive turns out to be wholly different.
Monica Davies is cut out of her father's will for her behaviour and sends him a letter to say that she is about to come into a large amount of money nevertheless. The trail leads the Protectors to Austria where Monica is involved in a kidnap plot whereby a number of skiers are unknowingly held to ransom at the top of a mountain and the authorities are only able to guess the terrorist's identity from their voice.
The holidaymakers are released after the ransom is paid and the Protectors join forces with Inspector Luhrs to try and work out which of the people in the party may have been involved in the terrorist group. Having done this they also have to find the possible link with Monica's letter and the extent of her involvement.
The poorly Mrs. Douglas enlists the aid of the Protectors after her young son Stephen is caught apparently smuggling a large amount of drugs in his back pack. When Harry goes to see Stephen in a Spanish jail the boy refuses to help himself but Harry is convinced that he is under the influence of Raphael Santana, the real drugs baron, and sets out to prove the link between the two.
A dissident Russian author is smuggled out of Russia into Britain, along with the manuscript of his book, which is severely critical of the Communists' political regime. Harry is hired to look after him but a pro-Communist group, anxious to burn the manuscript, come after and capture both men, requiring the intervention of Caroline and Paul.
Harry is amazed when an old friend of his whom he had assumed to be dead turns up in London. The man's 'death' was actually staged and is linked to a complicated and lucrative insurance fraud. This, in turn, leads Harry and Caroline to Venice, where the man is killed, this time for real. He has, however, left behind a letter which the Protectors must understand to scupper the deadly scam.
The Protectors are hired by the Hungarian actress Ilona Tabori, who wants them to help her take her father's body through the Iron Curtain and back to his natal village, where it was his wish that he should be buried. The funeral is successfully accomplished but Harry has had misgivings about this assignment all along and he could be proved right as it transpires that Ilona has another agenda to the one for which she first hired them.
Harry is pleased to meet up again with an old college friend of his, Zeke, who is playing jazz piano in a local night club. Unfortunately Harry is unaware that Zeke's sudden re-entry back into his life is no coincidence. In actual fact Zeke is being blackmailed by mobsters with whom he has got into debt into setting Harry up as a target for his enemies. Will Zeke be able to go through with it or will he save his old friend from his fate?
In Venice the Protectors come to the aid of an old friend of Caroline, Lena Hayden, an investigative journalist. She has reason to believe that a supposedly respectable local politician was actually involved in a murder. Her suspicions place her life in danger and require the Protectors to seek out a man who is believed to be long dead to assist her case.