The unreliable narrator, Latimer, believes that he is cursed with an otherworldly ability to see into the future and the thoughts of other people. His unwanted "gift" seems to stem from a severe childhood illness he suffered while attending school in Geneva. Latimer is convinced of the existence of this power, and his two initial predictions do come true the way he has envisioned them: a peculiar "patch of rainbow light on the pavement" and a few words of dialogue appear to him exactly as expected. Latimer is revolted by much of what he discerns about others' motivations.
Latimer becomes fascinated with Bertha, his brother's cold and coquettish fiancée, because her mind and motives remain atypically closed to him. After his brother's death, Latimer marries Bertha, but the marriage disintegrates as he recognizes Bertha's manipulative and untrustworthy nature. Latimer's friend, scientist Charles Meunier, performs a blood transfusion from himselfto Bertha's recently deceased maid. For a few moments the maid comes back to life and accuses Bertha of a plot to poison Latimer. Bertha flees and Latimer soon dies as he had himself foretold at the start of the narrative.