Hastings fulfills a classic role in the murder mystery genre as a foil to the great detective. Like Sherlock Holmes's Watson, Hastings is a man of ordinary intelligence who represents the average point of view. This gives Hercule Poirot a chance to explain himself and his thinking, so that the less intelligent Hastings (and the reader) can get a fuller understanding of Poirot's superior insights and abilities.

For example, in the first chapter, Hastings has just returned from dealing with issues at his South American home when he discovers that Poirot has received a letter from a man informing him that he is about to murder someone. Hasting represents the average point of view--and the police perspective—when he dismisses the letter as a hoax, but Poirot's strong feeling, based on his years of experience, that this might be real leads the reader to be worried.

Interestingly, in four different chapters in the mystery, Hastings moves to third-person narration of scenes that he was not part of. These function to cast suspicion on Cust, an epileptic man whom we are lead to believe might be the murderer.

In the end, Hastings's incomplete knowledge of what is going on makes him the perfect narrator for building suspense. He is with Poirot through much of the action, but he lacks Poirot's ability to interpret the evidence that they both see. Therefore, he functions much like the reader: witnessing what is going on but not knowing what it means.