When Simon murders Linnet, he improvises at the crime scene by using Linnet’s finger to write the letter J in her blood. In this case, Simon seems to have been trying to confuse the investigation, throwing suspicion toward his accomplice Jacqueline because he knew she had a perfect alibi. But the action also references a practice found in some old detective stories (and even current ones), where a dying victim leaves a sign that points to their killer. This echo is interesting because it suggests that the characters in the story are themselves familiar with the tropes of detective fiction. Simon, then, is trying to use the tropes of detective fiction to his own advantage. Unfortunately for him, however, Poirot is equally familiar with the conventions of the genre and considerably smarter—he realizes quickly that the J is a detective novel trope and, therefore, that it is a deliberately planted false clue (although he does not immediately know who the killer is). By specifically referencing a cliché of detective fiction, the J becomes a symbol of Christie’s own proclivity to play with her audience’s expectations, to twist or even upend certain expectations while at the same time fulfilling others.
The timeline below shows where the symbol The Letter “J” appears in Death on the Nile. The colored dots and icons indicate which themes are associated with that appearance.
...point-blank to the head while Linnet was asleep. Poirot finds this shocking because he suspects Jacqueline but feels that such an act does not fit her psychology. Poirot then notices that... (full context)
...the previous night, and then afterward tells a hypothetical version of the murder in which Jacqueline murders Linnet. Dr. Bessner, however, claims this version of events is not possible. To begin... (full context)