The Thumb Mark of St. Peter by Agatha Christie

The Thumb Mark of St. Peter is probably my favorite Miss Marple story from The Thirteen Problems collection and a big reason for that is quite simple: she’s the one presenting the mystery this time. Any story that gives Miss Marple the floor is already off to a strong start. Like Hercule Poirot, she’s one of those classic Agatha Christie creations with a very distinct personality and her own brilliant approach to crime-solving. She may look like an unassuming elderly lady from a sleepy village who enjoys knitting, but don’t let that fool you! Her understanding of human nature, sharpened by decades of village life, makes her surprisingly formidable.

One of the pleasures of this story is just listening to her talk. Miss Marple’s dry wit, sly observations, and gentle little quips are genuinely funny, especially when you realize she’s usually the smartest person in the room and knows it. She doesn’t bulldoze her way through a mystery; she sidles up to it, smiling pleasantly the whole time. She even takes a break at one point in her narration to focus on her knitting. Classic Miss Marple. 

The mystery itself revolves around her niece, who was stuck in an unhappy marriage before her husband suddenly dies several years later. Miss Marple casually notes that there’s “insanity in the family,” and before long, rumors ripple through the village that the wife poisoned her husband. Perhaps with arsenic or poisoned mushrooms. On paper, the setup sounds fairly straightforward, even a little mundane.

However, the real fun here isn’t the plot itself; rather, it's the way Christie structures it. Miss Marple slowly feeds the group (and us readers) a series of small clues, hints, and suggestive details as the story unfolds. Nothing is emphasized too heavily, and no single fact screams “this is important!” Instead, Christie plants information that seems incidental at first, trusting the reader to tuck it away. For example, what does fish and the marks of St. Peter's thumb have to do with providing the answer to the husband's mysterious death? It’s classic Christie misdirection: you are given everything you need, just not in the order you expect, and not with any helpful flashing arrows pointing at the solution. 

As Miss Marple investigates, each observation adds another piece to the puzzle. You can almost feel Christie nudging the reader: Are you paying attention? Did you notice that detail? By the time the truth comes out, it feels less like a shocking twist and more like a satisfying click, when everything finally locks into place. The final reveal is admittedly a bit over-the-top, but somehow that only adds to the charm. It’s theatrical in that very Agatha Christie way and it works because the groundwork has been laid so carefully. Miss Marple, needles in hand, calmly dismantles the gossip, clears her niece’s name, and reminds everyone that appearances and village rumors are rarely the whole truth. Of course, watching her do it is an absolute delight.