Hercule Poirot
Poirot is a retired detective and a Belgian refugee in Essex, UK during WWI. He has had an illustrious career and is known far and wide and trusted by Scotland Yard (the city of London's police), as is evident from Detective-Inspector Japp's reception of him. Poirot is somewhat of a trickster and tends to keep everyone in the dark about his investigations while they are still ongoing. He is obsessively neat and is always rearranging rooms and fixing people's outfits when they are askew.
Arthur Hastings
Captain Arthur Hastings is the narrator of the novel. He ends up at Styles Court after a brief stint in a convalescent home, recovering from injuries he sustained during WWI, which is still ongoing during the events of the novel. Hastings fancies himself an amateur sleuth, but he is extremely insecure about his investigatory prowess and desperate for the approval of Hercule Poirot. Hastings is infatuated with Mary Cavendish, his friend John's wife.
Inspector-Detective Japp
Japp works for the Scotland Yard and is, at least in an official capacity, the lead detective on the Styles case. He trusts Poirot's judgment implicitly and is very grateful to have him helping out on the case.
Emily Inglethorp
Emily Inglethorp is the matriarch of the Cavendish family. She is a socialite and is heavily involved in fundraising for the war effort. Technically, she is John and Lawrence's step-mother, but she raised them from a very young age and they've always considered her their mother. She is known to be very generous, but her generosity also notoriously comes with strings attached. She is murdered by strychnine poisoning, and her murder is the subject of the novel.
Alfred Inglethorp
Alfred is Emily's new husband. He is twenty years her junior, and everyone in Styles Court suspects him of being a gold-digger. He is the first and primary suspect in Emily's murder.
John Cavendish
John is Emily's older son. He was a lawyer, but abandoned his practice to settle into life as a country squire. John's finances are tight, and since his mother remarried, she has not been as willing to provide for him. He lives with her at Styles Court until her death, when he is poised to inherit the estate. His position makes him a prime suspect after Alfred is initially cleared.
Lawrence Cavendish
Lawrence is John's younger brother. He studied to be a physician but abandoned his practice to write poetry. He is thought of by the others as brooding and dark.
Mary Cavendish
Mary is John's wife. She enjoys working in the garden and carries on an affair with Dr. Bauerstein. Marry explains to Hastings that she never really loved John, he was just a way out of her horrid life after being orphaned in her teens and ending up stuck in Yorkshire, living with her great aunts.
Dr. Bauerstein
Bauerstein is a neighbor to the Cavendish family. He is a world-renowned expert on toxicology and poisons. He carries out an affair with Mary Cavendish, but is later revealed to be a spy for Germany.
Evelyn Howard
Evelyn Howard is one of Emily's oldest friends. She also works at Styles Court and at a hospital thirty minutes away. Eve's pride has always prevented her from taking gifts from Emily. She is described as brusque and no-nonsense by the others.
Cynthia Murdoch
Cynthia works at the dispensary of a hospital, much like Agatha Christie did while she was writing this novel. Cynthia is young and dependent on the generosity of her Aunt Emily, who promises her that she'll be provided for in the event of her death. Hastings finds Cynthia quite charming, and even proposes to her at one point in the novel, but she has affections for Lawrence Cavendish.
