Sundar Raj Kapoor, Radha Vyjayanthimala, and Gopal Rajendra Kumar have been friends since childhood. As they grow into adults, Sundar develops an obsessive devotion to Radha, seeing her as the only woman in the world, while Radha’s heart remains with Gopal, who loves her in return and steadfastly resists Sundar’s advances. Yet Sundar’s fierce loyalty to his friendship with Gopal is equally immense, and he confides his feelings to his friend, who resolves to sacrifice his own love for Sundar’s happiness.
Before Sundar departs for a dangerous mission with the Indian Air Force in Kashmir, he extracts a promise from Gopal: never let any man come between Radha and himself while he is away. Sundar carries out his mission, but his aircraft is shot down and he is listed as killed in action, later being awarded the Param Vir Chakra for bravery. The news saddens Radha and Gopal, yet it also momentarily frees them to openly express their love for one another. Among the notes of their happiness, Gopal writes an unsigned love letter to Radha that touches her deeply, and she keeps it close, hidden away.
When Sundar returns, alive and well, the self-effacing Gopal sacrifices his own feelings once more, stepping back so that Sundar can resume wooing Radha. Radha’s parents, who initially disliked Sundar, ultimately accept the match after his valor is publicly recognized. The couple then enjoys a long European honeymoon, and Sundar experiences delirious happiness. Radha, devoted to her husband, resolves to stay faithful and privately asks Gopal to stay away from their life, because his presence torments her.
Nevertheless, Sundar’s devotion to Gopal remains, and he tries to draw his friend back into their daily lives, much to Radha’s chagrin. The fragile balance shatters when Sundar accidentally discovers the unsigned letter. He confronts Radha with it, pulling a pistol and demanding the name of her supposed lover, but she refuses to reveal it. The days that follow bring Radha a living nightmare of jealousy, threats, and anxiety as she endures Sundar’s fixation on the letter.
Unable to bear the misery any longer, Radha flees to Gopal for help. Sundar tracks them down, and in a tense confrontation, Gopal finally admits authorship of the letter. Sundar asks why Gopal sacrificed his own love, and Radha chides both men for never considering her feelings in the name of their friendship. With no easy exit from the stalemate, Gopal takes Sundar’s pistol and kills himself. In the aftermath, Radha and Sundar are reunited, but they do so while mourning the loss of a steadfast friend.
