There is a striking similarity between Roald Dahl's "Lamb to the Slaughter" and Edgar Allan Poe's "The Purloined Letter." In Poe's short story the brilliant amateur detective C. Auguste Dupin states a truth which applies to "Lamb to the Slaughter" as well as to "The Purloined Letter."
“Perhaps it is the very simplicity of the thing which puts you at fault,” said my friend.
“What nonsense you do talk!” replied the Prefect, laughing heartily.
“Perhaps the mystery is a little too plain,” said Dupin.
“Oh, good heavens! who ever heard of such an idea?”
“A little too self-evident.”
In both stories the police are exhaustively searching for a item which they fail to see because it is right under their noses, "hiding in plain sight." In Poe's story the police are searching for a letter which has been "purloined" from an important person. It turns out that the letter, rather than having been concealed, had been slightly changed in appearance and placed in plain view in a card-rack. In "Lamb to the Slaughter" the police never think of the leg of lamb as a possible murder weapon because it is so obvious. Mary Maloney is cooking it in the oven and the tantalizing aroma permeates the entire house. In the end she actually succeeds in getting the hungry policemen to eat the murder weapon they have been looking for. If C. Auguste Dupin had been involved in the story "Lamb to the Slaughter," no doubt he would have deduced that Mary Maloney killed her husband with a frozen leg of lamb. The police are put off in both cases because of their predetermined conviction that the item they are searching for must have been very carefully hidden.