The Flock of Geryon

Hercule Poirot is reacquainted with Amy Carnaby, the companion from The Nemean Lion, whom Poirot praises as one of the most successful criminals he has ever met. She is worried as she constantly thinks of illegal schemes which she is sure would work and she fears she is turning into a hardened criminal. She wants to put her talents to good use and assist Poirot in fighting crime in any way she can. She also has brought to him a possible case in which she can prove herself.

She has a friend, Mrs Emmeline Clegg, a widow who is comfortably off. In her loneliness, Mrs Clegg has found comfort in a religious sect called "The Flock of the Shepherd", based in a retreat in Devon. Their leader, Dr Andersen, is a handsome, charismatic man. Mrs Clegg has made a will leaving all of her property to the Flock. Miss Carnaby is especially concerned as she knows of three women in a similar situation who have all died within the past year. She has investigated and found nothing unusual in the deaths, all of which were due to natural causes and none of them happened within the sanctuary but at the homes of the deceased. Poirot asks Miss Carnaby to infiltrate the sect. She is to pretend to be dismissive of them and then, once within the sanctuary, be persuaded to be a convert.

Poirot consults Japp. The Scotland Yard detective finds out that Andersen is a German chemist, expelled from a university there by the Nazis because he had a Jewish mother and that there is nothing suspicious about the deaths of the women whose names have been supplied by Miss Carnaby. Nevertheless, Poirot views Andersen as the monster Geryon whom he is determined to destroy. Miss Carnaby settles down at the sanctuary with Mrs Clegg and joins in a festival held at night – "The Full Growth of the Pasture". At the service, she is dismissive of the liturgy but suddenly feels a needle-prick in her arm. Almost instantly she starts to experience a feeling of well-being and euphoria which makes her sleep for a short while.

Poirot instructs her to tell Andersen that she is going to come into a large sum of money that she will leave to the Flock, that she has problems with her lungs, and that Mrs Clegg will soon inherit a large sum from an aunt, more than her present estate. Poirot also asks if she has met a Mr Cole at the sanctuary. Miss Carnaby has and to her he is a very strange man. As if to prove her assertion correct, soon afterwards Mr Cole accosts Miss Carnaby with tales of his strange visions which involve virgin sacrifices, Jehovah and even Odin. She is saved from further strange tales by the arrival of Mr Lipscombe, the lodge-keeper of the Devonshire estate.

The day before the next divine service, Miss Carnaby meets Poirot in a local teashop. She seems to have had an about-face and tells Poirot that Andersen is a great man and that she cannot betray him. She rushes out of the shop and Poirot sees that a surly-looking man has been listening in to their conversation. The next service is proceeding and Miss Carnaby is about to be injected again when Mr Cole steps in. There is a fight and the police pour into the room. Mr Cole is in fact Detective Inspector Cole and he arrests Andersen.

Later the parties confer. The man in the teashop was Mr Lipscombe and when Miss Carnaby recognised him, she put on an act of allegiance to Andersen. Poirot realised this when he had the man followed back to the lodge. Andersen's chemistry background (although he was probably not a Jewish refugee) came in useful for preparing injections of hashish to produce ecstasy in his adherents, and also for injecting them with relevant bacteria when he wanted to kill them and inherit their estates. Andersen was about to inject Miss Carnaby with tuberculosis bacteria to tie in with the fictional ailment she told him about. The proof has been obtained in the laboratory in the sanctuary that the police have raided.