The film opens with a car skidding off an icy road, setting a tense tone for the story. Coleman Silk, played by Anthony Hopkins, is a distinguished professor who has rejuvenated the academic life at Athena, a quaint New England college. During a classroom discussion, he refers to two absent students as "spooks," which leads to accusations of racism. This incident forces him to resign, an event that devastates his wife, leading to a heart attack.
Believing the institution is responsible for his wife's demise, Silk forges an unlikely friendship with a struggling writer, Nathan Zuckerman (Gary Sinise). Together, they embark on a writing project that aims to expose the circumstances surrounding the tragic event, helping Zuckerman rediscover his voice. However, Silk eventually decides to abandon the book and begins to reflect on his past.
In a nostalgic flashback, we see the younger Silk ([Wentworth Miller]) fall in love with Steena Paulsson ([Jacinda Barrett]). The film then shifts back to present day, where Silk is entangled in a secret affair with a considerably younger woman named Faunia Farley (Nicole Kidman). After rescuing her from being stranded, Faunia makes a bold advance towards him. As they spend time together, she reveals her troubled past, including childhood trauma inflicted by her stepfather and her tumultuous relationship with her unstable ex-husband, Lester (Ed Harris), who relentlessly stalks her.
Tensions rise when Lester confronts Silk, accusing him of being a bad influence on Faunia, ultimately revealing deep-seated issues from Faunia's past, including the tragic death of her children in a fire—an event that continues to haunt her. Faced with threats and uncomfortable truths, Silk's lawyer likens him to Achilles, hinting at the sacrifices made in the name of love. Silk reacts fiercely, leading to a breakdown in their professional relationship.
As the narrative unfolds, we learn about Silk’s complex identity. His boxing trainer once pushed him towards the sport for monetary gain, revealing the irony of Silk, who is actually of mixed race yet perceived as white due to his light skin. His father had high hopes for him, dreaming of a career as a doctor, but after losing him, Coleman grapples with societal and racial disparities.
Tension escalates between Silk and Zuckerman as rumors surface regarding Silk's affair. Overlapping scenes show Silk's relationships with both Steena and Faunia. During a classical concert, Silk encourages Faunia to confront her fears about commitment, yet their relationship is tumultuous. After a heated confrontation, she leaves, only to return later apologizing after expressing her guilt over her past.
Tragically, their story culminates in a fatal confrontation with Lester, who deliberately runs them off the road, leading to their untimely deaths. In a twist of fate, Lester insists during a therapy session that he did not intend to kill them, though his intentions were clear.
At Coleman’s funeral, his colleague Herb ([Ron Canada]) finally acknowledges his failure to support Silk during his struggles. Zuckerman meets Ernestine ([Lizan Mitchell]), who claims to be Silk’s sister. Through her, he learns of the familial estrangement imposed by Silk’s choices regarding identity and race. With newfound determination, Zuckerman sets out to document Silk's story, leading to the creation of his book, The Human Stain, a poignant exploration of race and identity in a world riddled with prejudice.
