Dr James Sheppard is the narrator of the story and the village doctor. He lives with his sister and is trusted by everyone. He acts as confidant to Ralph Paton and Ackroyd and is a replacement for Hastings to Poirot. He accompanies Poirot during most of his investigations and enquiries; showing amazement, curiosity and ridicule for his method in equal measure. After reading his notes on the case, Poirot remarks that he is too reserved, keeping himself mostly in the background. His reticence has a more sinister purpose than one suspects. When Poirot reveals Sheppard to be the blackmailer and murderer, his reserve in the narration is no longer a sign of modesty. It is a manipulative tactic to waylay readers while speaking (a part of) the truth.
This is a man who writes about a murder and participates in the investigation, without giving himself away. He is a morally weak man who breaks his Hippocratic oath to hide the true diagnosis of Mr Ferrars’ death for his own profit. Moreover, he simply gambles away the twenty thousand pounds he extorted from Mrs Ferrars. Behind the façade of the friendly neighbourhood doctor is a calculating murderer and an egomaniac who participates in the investigation against himself, confident of getting away. In the end, his crimes and lies catch up with him. Ironically, he ends his life in the same way as Mrs Ferrars, whom he drove to suicide. He rejects a symbolic reading of his end, claiming he doesn’t pity either her or himself to validate the idea of poetic justice. Till the end, there is no sign of repentance. His only reason for choosing death as an alternative is to protect his sister from the shock and disgrace of his actions.