In Spain, young David Mitchell, son of a wealthy man, has joined an extreme revolutionary group and taken as a hostage Anna De Santos, a childhood friend. The group intend to blow up a bridge as an American diplomat passes over it. The Protectors are alerted and Harry masquerades as an explosives expert supposedly about to assist the group with their plan in order to infiltrate them.
In the heart of the Home Counties business man Sir Charles Standish receives kidnap threats against his teen-aged daughter Vicky, possibly by aggrieved former business associates. Rather than involve the police and panic Vicky, Standish engages the Protectors but things must look as normal as possible and so Harry is passed off as her new tutor though he does not have the easiest of times with her.
Wealthy Canadian Adam Ferris gets in touch with the Protectors when his heiress daughter Anne goes missing in London and turns up again having joined a religious sect with sinister overtones of the occult. Ferris is concerned that the group will brain-wash her into giving them her considerable inheritance. Harry poses as a reforming alcoholic in need of spiritual guidance in order to join the sect.
Caroline is asked by British Intelligence to act as a 'goat' to act as decoy to catch a 'tiger'. An ex-boyfriend of hers is a spy and she is told that he is the potential victim of an assassination plot, which she is brought in to foil. However, when the man tells her that he has resigned as an agent, Caroline sees that she has been employed under false pretences. She is indeed a decoy and only Paul can save her.
Harry is on the trail of one of the largest heroin smuggling operations, a trail which leads him from London to Denmark where he comes to on a landfill site to discover that the gang involved in the smuggling has eluded him. However he is aware of the harbour port where the drugs are being stashed and, as he is the only man apart from the miscreants, who knows its location, it puts him very much in danger.
Anne Gordon seeks the help of the Protectors. Her son John is on trial for a crime that he did not commit though her fears are actually for her husband Arthur. He is a disturbed mental patient who has gone missing after hearing about the trial. The judge in charge of John's case is Judge Cronin and the Protectors must prevent Arthur from killing him.
Harry is on a train returning from Edinburgh to London. He gets into conversation with a fellow traveller. This man is the poetic Shadbolt, but there is something about him that Harry cannot possibly know. Shadbolt is also a professional assassin and his presence on the train is no coincidence. He has been paid to kill Harry at a given time, a fact to which Harry must tumble for the ultimate show-down.
Carrie Blaine is a professional singer about to make her come-back. However she is convinced that her house is haunted when the clocks start to run backwards and she keeps hearing a chorus of children singing 'A Pocketful of Posies'. Is she correct in her guess or is she about to have a break-down? Or is she being used as part of a sinister plot by one of her associates? Enter the Protectors to find out.
Harry joins a car rally as a driver whilst the Protectors are in pursuit of their toughest case to date. A Swiss bank hires them to go after stolen papers but they only want the copies, not the originals. This involves cracking a safe, photographing the contents of a locked brief-case - the details of a numbered bank account - and returning them to the bank without the account holder knowing that anything has happened.
All the copies of a film have been stolen at the pre-production stage and Harry is called in by its director to try and recover them. Whilst they are talking in his office, they are joined by the alleged thief, who offers to return the prints in exchange for a ransom. The money is duly paid and the blackmailer steps into the lift. However, he is not seen to get out again, or to leave the building. How did he vanish into thin air?
A gang of hi-jackers led by villains Birch and Slater are making off with security vans containing consignments of platinum in different European locations and the Protectors are called in to stop them. However the assignment is no easy task as the evidence, namely the vehicles containing the booty, seem to disappear. Could an old chemistry set experiment hold a clue as to what is happening?