Two childhood sweethearts, Shankar, [Dharmendra], and Bhawariya, [Sharmila Tagore], are torn apart in their youth by cruel circumstances. Shankar grows up to be a rough, undereducated hunter, while Bhawariya becomes Madhumati, a traditional and beautiful woman.
Shankar's cousin, Suresh, [Deven Verma], is a well-educated advocate. When marriage proposals come for both Shankar and Suresh, family traditions dictate that the boys cannot meet their own brides, but they are allowed to see the other boy's intended bride. Shankar’s proposal is for Madhumati, while Suresh’s is for Shaanta [Shashikala]. Shankar sees Shaanta and believes she could suit his cousin, but Suresh is immediately drawn to Madhumati and schemes to win her for himself by deceiving both Shankar and Madhumati.
He crafts two anonymous “poison-pen” letters to the families of the prospective brides, maligning both Shankar and himself in a calculated bid to derail the engagements. Shaanta's family, impressed by Shankar’s character when they meet, agrees to give her hand to him, unaware that he is less educated than they suppose. Suresh, posing as a martyr, agrees to marry Madhumati, achieving his hidden goal.
On the wedding night, Shaanta discovers the true extent of Shankar’s supposed lack of education and feels betrayed, triggering a rift in their relationship. As the letters’ details emerge, everyone, including his parents, suspects Shankar of writing them out of jealousy. Feeling isolated and heartbroken, Shankar finds solace in Madhumati, who has become his cousin’s wife and acts as his supportive Bhabhi.
Accidentally, Shankar learns that Madhumati is actually his long-lost childhood sweetheart Bhawariya, a truth he chooses to keep to himself. Meanwhile, Madhumati’s brother, a handwriting expert, uncovers Suresh’s wicked plot and the real origin of the letters. He confronts Suresh, but Shankar overhears the confession, setting off an emotional confrontation that ends with Suresh’s accidental death.
Shankar is unjustly blamed and charged for the tragedy. Madhumati initially desires to see her husband’s killer punished, even hanged. Yet at the trial, she ultimately changes her testimony at the last moment, a decision that saves Shankar from conviction. The verdict delivers his acquittal, but the ending is bittersweet and ironical: Shankar remains silent about his true identity as Madhumati’s childhood love, bearing that secret alone.
