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The Thumb Mark of St. Peter is a short story written by Agatha Christie and first published in The Royal Magazine in May 1928 in the UK. In the U.S., the story was first published in Detective Story Magazine in July 1928. It is the sixth short story of the Tuesday Night Club story arc.

In 1932, the story was gathered and published as the sixth short story collection The Thirteen Problems. It is preceded by Motive v. Opportunity and followed by The Blue Geranium.


At the sixth meeting of the Tuesday Night Club, it is Miss Marple's turn to present her mystery. This concerns the death of a man whose last words concerned "a pile of carp."

Plot summary

(may contain spoilers - click on expand to read)

The final story to be told at the regular meeting of the Tuesday Night Club comes from Miss Marple herself. It concerns a niece of hers called Mabel who obstinately married Geoffrey Denman when she was twenty-two, despite Denman having a violent temper and there being a history of insanity in his family. Ten years later he died and Miss Marple wrote to offer to stay with her for while but received a reply back that politely refused the offer. Three months later a second letter was sent to her aunt hysterically begging her to come.

Arriving at her niece’s house which Mabel shares with two servants her 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 murdered her husband and no one in the area would now talk to her. Geoffrey had been taken ill in the night and died soon after the doctor arrived but the old locum had not raised the alarm about the manner of death. It was thought that he had died after eating poisoned mushrooms. The two servants told Miss Marple that Denman had been unable to swallow and was rambling before he died about fish. An exhumation order was granted followed by an autopsy that proved totally inconclusive. Miss Marple began to wonder if Geoffrey had committed suicide and used a knowledge of medicine gained in a previous period of his life to do so. 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". She realised that the solution lay in the mysterious words uttered by Geoffrey as he lay dying. 

Questioning the servants further, they stated that the words were to do with a "heap" or "pile" of some fish whose name probably began with "c". Checking a list of poisons, Miss Marple found one called Pilocarpine and read that it is also an antidote for atropine poisoning. Based on her own eyedrops which contain atropine sulphate she confronted the elderly Mr. Denman and accused him of murdering his son. The old insane man laughingly confessed the crime, committed because he overheard his son planning to put him in an asylum. He emptied his eye solution into his son’s bedside glass of water knowing that Geoffrey would drink it in the night. 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. His aunt corrects him – she knows that he proposed to Joyce earlier in the evening!



Research notes

Film, TV, or theatrical versions

When Greenshaw's Folly was adapted for Agatha Christie's Marple, starring Julia McKenzie, the plot of The Thumb Mark of St. Peter was also woven into the story.

Publication history

  • 1928: The Royal Magazine (London), issue 355 May 1928 - with illustrations by Gilbert Wilkinson.[1]
  • 1928: Detective Story Magazine, Street & Smith (New York), Volume 102 Number 4, 7 July 1928.
  • 1930: Hush, vol. 2 no. 9, Feb 1931.
  • 1932: The Thirteen Problems/The Tuesday Club Murders
    • 1932: Collins Crime Club (London), June 1932, Hardcover, 256 pp
    • 1933: Dodd Mead and Company (New York), 1933, Hardcover, 253 pp
    • 1943: Dell Books (New York), Paperback, (Dell number 8)
    • 1953: Penguin Books, Paperback, (Penguin number 929), 224 pp (under slightly revised title of Miss Marple and the Thirteen Problems)
    • 1958: Avon Books (New York), Paperback (Avon number T245)
    • 1961: Pan Books, Paperback (Great Pan G472), 186 pp
    • 1963: Dell Books (New York), Paperback, 192 pp
    • 1965: Fontana Books (Imprint of HarperCollins), Paperback, 192 pp
    • 1968: Ulverscroft Large-print Edition, Hardcover, 207 pp ISBN 0-85456-475-6
    • 1972: Greenway edition of collected works (William Collins), Hardcover, 222 pp
    • 1973: Greenway edition of collected works (Dodd Mead), Hardcover, 222 pp
    • 2005: Marple Facsimile edition (Facsimile of 1932 UK first edition), September 12, 2005, Hardcover, ISBN 0-00-720843-X
  • 1964: The Saint Mystery Magazine (UK), vol. 9 no. 11, Jan 1964.
  • 1967: Ellery Queen's Mystery Magazine, vol. 49 no. 6, whole no. 283, Jun 1967, as "Ask and You Shall Receive".