As well as the old lady herself, there is her nephew – the writer Raymond West – the artist Joyce Lemprière, Sir Henry Clithering (a former Scotland Yard commissioner), a clergyman called Dr Pender, and Mr Petherick, a solicitor.

Mr Jones was a commercial traveller; a maid in one of the hotels in which he stayed saw blotting paper he had used to write a letter, whose decipherable phrases referred to his dependency on his wife's money, her death, and "hundreds and thousands".

Miss Marple witters on about a similar case involving a local family (to which Raymond cannot see any relevance) until she suddenly asks Sir Henry if Gladys confessed, and says that she hopes Mr Jones will hang for what he made the poor girl do.

It took place at a house on the edge of Dartmoor called "Silent Grove" which was newly purchased by Sir Richard Haydon, an old college friend of the doctor's.

Travelling by train to Newman's house in the village of Polperran, Raymond shared a carriage with Police Inspector Badgworth who knew of the Spanish treasure trove but was specifically interested in the more recent wreck of a ship called the RMS Otranto.

The latter sank six months earlier and its bullion had either been removed from the ship's strongroom after the hull had been torn open on the rocks of Serpent's Point, or stolen some time before.

As Joyce worked on her canvas she overheard the conversation of the three people, and Denis's suggestion of hiring a rowboat to take them round the coast to a local cave.

Two days later, she read in the paper that Margery had disappeared while bathing in the sea, and a week later her body was found washed up with a blow to the head, supposedly caused when she dived into the water on some rocks.

A Scotland Yard inspector was already there investigating Denis who, under several names, had married women, insured their lives for large sums, and then killed them in a conspiracy with Carol – his real wife.

Alarmed by this, Mr Petherick visited his client and then suggested to Grace's husband, Philip, that a noted professor on the subject of spiritualism be invited to the house to witness the séances.

Arriving at her niece's house, which Mabel shared with two servants – hers and a nursemaid for her mentally-ill father-in-law – Miss Marple learned that the widow was the subject of gossip to the effect that she had murdered her husband, and no one in the area would now talk to her.

Totally stumped by the problem, she was in the high street and in something of a silent prayer for guidance when she opened her eyes and saw a fresh haddock in the fishmonger's window with its characteristic black spots known as the "thumb mark of St. Peter".

Mr Denman is committed to an asylum after all and the Tuesday Club congratulates Miss Marple on her success, although Raymond points out there is one thing she doesn't know.

Asked for suggestions as to a sixth person for dinner, he names Miss Marple and tells an incredulous Dolly of her success at solving last year's mysteries.

Before she left Gran Canaria ten days later, Miss Barton asked Dr Lloyd several strange questions regarding the justification of taking the law into one's own hands.

His household comprised his niece Greta; an old servant, Gertrud; a local gardener Dobbs; and Dr Rosen's secretary, Charles Templeton, whom Clithering reveals was one of his own men, put in the house to keep an eye on things (but possibly not totally above suspicion).

Miss Marple and Mrs Bantry point out that the three people in the letter and the one place name, together with the word "Honesty", are all species of dahlias and that, rearranged, they spell "Death".

Miss Marple's feelings were confirmed when she shared a tram ride with the couple and witnessed Mr Sanders "tripping" on the stairs onto his wife who then fell down, but was fortunately saved by the conductor.

It was Sylvia herself who picked the foxglove leaves and Dr Lloyd wonders if the intended victim was Sir Ambrose, who was prescribed drugs for his heart condition.

Someone calling herself Miss Kerr had rung up the police, told them the bungalow had been burgled, and described Leslie Faulkener as having visited there earlier that day, but having been refused admittance.

Some time has passed since the six people met at the Bantry home, and Sir Henry is once again a guest there when news reaches the house early one morning that a local girl called Rose Emmott has been found drowned in the river near to the mill.

Later in the morning, Sir Henry receives a visit from an upset Miss Marple who tells him that Rose was murdered, and she doesn't want the wrong man to be hanged for the crime.

Sir Henry, defeated in his attempt to clear Sandford, visits Miss Marple, who tells him Mrs Bartlett couldn't have been home on a Friday – the night in question.

"[6] Isaac Anderson in The New York Times Book Review (5 March 1933) wrote: "The stories are slight in structure, but they present some very pretty problems and introduce us to some truly interesting people.

Incredibly self-centred and difficult, she preferred to surround herself with men whom she then expected would accede to her demands and whims, such as brushing her hair or walking miles to purchase her favourite confectionery, which she would then eat in one sitting, making her sick.

[12]: 298–299  Christie refers to this incident in Death in the Clouds (1935) and, even more pointedly, based the character of the doomed, unstable Louise Leidner in Murder in Mesopotamia (1936) on Katharine.

[11]: 210 The blurb on the inside flap of the dustjacket of the first edition (which is also repeated opposite the title page) reads: The appearance of Miss Marple in Murder at the Vicarage provided detective fiction with a new and distinctive character.

Miss Marple, that delightfully clever village spinster who solves the most amazing mysteries quietly and unobtrusively from her chair by the fireside, appears in each of the stories comprising The Thirteen Problems.

Elements from The Thumb Mark of Saint Peter were combined with Greenshaw's Folly for the sixth series of Agatha Christie's Marple, starring Julia McKenzie, first airing 20 June 2013.

[14] Elements from The Herb of Death were woven into the Agatha Christie's Marple adaptation of The Secret of Chimneys, starring Julia McKenzie, which first aired 20 June 2010.