Murder’s abound in this novel and yet the solving of the murders takes second place to Poirot’s attempts to thwart four evil geniuses who have come together to form the most powerful criminal coalition the world has ever seen.

From time to time Agatha Christie would pen a novel that was aimed at being a thriller rather than the conventional murder mystery novel with which she has become synonymous. Perhaps unusually it is Poirot who is the main character rather than other more energetic characters such as Tommy and Tuppence Beresford or Lady Eileen "Bundle" Brent, who tend to feature in other Christie novels of this kind.

This isn’t one of Agatha’s classics. If anything the plot is so fanciful and melodramatic that it is hard to see any resemblance of realism. This is a hotchpotch of themes, characters and plot lines taken from some more sensational fiction. Sherlock Holmes meets Fu Man Chu with a bit of Dick Barton thrown in for good measure.

The Big Four consist naturally of 4 larger than life characters whose sole aim is to bring an end to civilisation as we know it. As the members of The Big Four are unveiled it is hard to understand what personal advantage there would be for any of them if they were ever to achieve this goal; but I’m getting ahead of myself ………..

Back from South America where he lives with his wife “Cinderella” Captain Hastings is keen to see his great friend Hercule Poirot once again. Poirot now spends his time as a 'consulting detective', investigating only those cases that interest him. Rather like Holmes !

Arriving at Poirot’s abode Hastings discovers that his friend is about to depart for Rio to investigate a case. The money being too good to resist … even for Poirot. The client American Abe Ryland, is the richest man in the world. Also known as the 'Soap King', Ryland suspects that something underhand is going on at his company in Rio and insists that Poirot be on the spot to investigate.

Suddenly, the door opens to the bedroom to reveal a man in a highly disturbed state. He is emaciated, filthy and very disorientated. He keeps repeating Poirot's name and address, and seems unable to say anything else. When given a pencil and piece of paper, he scribbles the figure 4' over and over again. Poirot believes this alludes to an international gang of criminals known as the 'Big Four'. As proof of this when Hastings mentions the Big Four within the mans hearing it has a strange effect. He sits bolt upright and says the name – ‘Li Chang Yen'. Then, as if giving a lecture or reciting from a document, he goes on to list certain facts about the group known as the Big Four.

This has to be one of the strangest plot lines in the book, but it does give the character the opportunity of telling us more about the Big Four. Li Chang Yen is Number One - is the criminal genius who controls the organisation, and he is aided in his evil machinations by Numbers Two, Three and Four. Number Two is said to provide the financial backing for the Big Four, but the only thing known about Number Three is that she is a French woman. When it comes to Number Four's role in the gang, the man hesitates, apparently constrained by terror, but manages to gasp out two words before fainting dead away - 'the destroyer'.

At this point Poirot has to leave for Brazil, apparently leaving a complete stranger in his rooms !! However during the first leg of the journey on which he is accompanied by Hastings, Poirot beginning to suspect a trick to get him out of the way, abandons the trip and sets of for home. When Poirot and Hastings arrive back at the lodgings the stranger is dead. Eventually it is discovered that he has been murdered. The weapon is also one of the most unusual used by Agatha – Poisonous vapours, which make the death appear to be as the result of natural causes.

A clue to his identity soon surfaces when a man calls at the flat saying that he is from an asylum and that one of his patients, who has escaped, has been traced to Poirot's rooms. He claims that his patient suffers from persecution mania and believes that Chinese secret societies have imprisoned him in the asylum. Poirot asks if anyone ever considers that the man might be telling the truth. The caller remains sceptical, commenting: They all say they're sane.'

After the man has departed, Poirot observes the clock, which has stopped at four o'clock. Poirot believes this to be a final message from the dying man, naming his killer as Number Four, the 'destroyer'. Again, to most readers, there must have been an easier way to relay this message rather than this very melodramatic method. Indeed anytime the number four appears it always give an over sinister interpretation, given its regular occurrence in day to day life coincidence could be the cause, but it is never considered.

Inspector Japp recognises the dead man in Poirot’s rooms as a Secret Service agent
who disappeared while in Russia.

Poirot decides to telephone the asylym to obtain further information only to discover that there are no patients missing. The visitor then, was an impostor, almost certainly Number Four in disguise revisiting the scene of the crime. Poirot's interest is now fully roused, and he sets out to track down the Big Four.

His first port of call is the house of John Ingles, a retired civil servant and expert on China. Ingles is able to tell Poirot that Li Chang Yen, Number One of the Big Four, is a man of great intelligence who satisfies his lust for power by inciting revolutions and unrest on a global scale. Ingles even suggests that the Russian Revolution was instigated by this sinister and mysterious mandarin, who used Trotskv and Lenin as his puppets.

Ingles has recently received a letter from a man begging for money to help him escape from the Big Four. Ingles had believed the man to be mad but Poirot is concerned. Together they head to
Dartmoor from where the letter was sent. But yet again Poirot has been beaten to it by the Big Four. and he finds the sender of the letter dead.

As Poirot's investigations continue, the trail of the Big Four leads him through a succession of baffling mysteries. Although apparently unrelated. these cases invariably have all the hallmarks of the ruthless gang. Particularly the elusive Number Four who always seems to be one step ahead of Poirot. The Big Four prove time and time again that they will stop at nothing to achieve their aims and that they have no qualms about eliminating anyone who tries to stand in their way.

Can Poirot save the world or will the Big Four prevail, eliminating Poirot in the process. While I have no intention of spoiling the book for those yet to read it, one of the most frustrating things is the Big Four’s apparent desire to kill Poirot yet there are several occasions when a simple opportunity presents itself and they fail to take it. Will they run out of chances?

As I said at the start this isn’t one of Agatha’s best, and maybe the disappointment is even greater given that this was the next book to be published after the fantastic and intriguing “The Murder of Roger Ackroyd”. I can’t help feeling that readers at the time must have felt the same.