Hercule Poirot
Hercule Poirot himself is symbolic of the way that having a unique outsider's perspective can shake up an investigation—and community. Using his charm and deductive reasoning skills, Poirot is able to look at the community in which Joyce was murdered in a different way that allows him to gain clarity on the culprit's potential motivations.
The inheritance
The inheritance that Miranda is set to get is a powerful symbol of the lengths people will go to in order to get money. In fact, Garfield murders Leslie Ferrier and Joyce Reynolds so he can access Miranda's inheritance.
Control
Garfield's desire to control the people around him is a common motif in the novel. That control manifests in Garfield murdering people, especially Joyce Reynolds, whom he murders to keep her quiet and control the narrative surrounding Miranda and Leslie.
The drowned witch
Mrs. Oliver listens to a story about a woman who was drowned because people around town called her a witch. The story of the witch becomes symbolic of unjust accusations and the consequences of beliefs that aren't backed up by facts.
