Plot
Ravi Khanna (Amitabh Bachchan) is a common man working as a travel agent and living happily with his widowed mother (Sulochana Latkar), wheelchair-bound sister, Renu (Farida Jalal), and younger brother, Billu (Alankar Joshi). He is also due to get married with his girlfriend, Neela (Parveen Babi), who is the only daughter of a wealthy man, Mr. Rajvansh (D. K. Sapru). One night, a wealthy client, Surendra Sinha (Rehman), visits Ravi's office to collect the air tickets that have been reserved for him. Ravi notices a large emerald ring on the finger of Surendra, who also offers him a lift in his car as it is been raining heavily. Later, Ravi learns from the police that Surendra was apparently kidnapped that same night, and that the kidnappers have demanded a ransom of ₹5 lakhs to Surendra's younger brother, Narendra Sinha (Satyen Kappu). Narendra has agreed to pay the ransom to save his brother, but there is no news about Surendra again. Six months later, CID Inspector Khurana (Iftekhar) and Inspector Kulkarni (Jagdish Raj) shockingly discover Surendra's dead body in a gutter, and visit Ravi's office for interrogation regarding the murder. Ravi is nervous for Khurana and Kulkarni taking a keen interest in him, since he is the last known person to have encountered Surendra. He believes himself to be having an alibi and seeks legal advice from his lawyer friend, Advocate Rane (Shiv Kumar), for being a simple man with a family to be taken care of, and wanting to do nothing with the police and the courts.
However, the stress seems to be triggering several headaches which causes Ravi intense pain for a couple of minutes. After a second episode, he takes it serious enough to visit Dr. Shah (Sajjan) and undergoes an X-ray of his brain. The shocking diagnosis is that Ravi has a brain tumour that needs to be removed through a brain surgery, and if not, will cause his death within six months. Ravi is willing to undergo the brain surgery, but Dr. Shah states that it could either cure him completely, or could result in very unintended side-effects from blindness to mental illness to paralysis. Ravi is shattered for having many responsibilities on his mother, sister and brother, and feels that he has no right to die or become a burden on them. As a result, Ravi leaves without making a decision when the choices are death and a life worse than death. At the same time, he receives the interesting news of the grieving Narendra having declared a handsome reward of ₹5 lakhs (which he was previously ready to pay to his brother's kidnappers) to the person who will help him capture Surendra's murderer. In an attempt to better his family's financial conditions after him, Ravi plans to frame himself for Surendra's murder and collect the reward money for his family, believing that he has nothing to lose and is going to die in six months nevertheless. He telephones Khurana and Kulkarni at the police station as an anonymous informer about Surendra's murder, who declares Ravi as the culprit and instructs the police to deposit the money with his lawyer, Rane.
A desperate Narendra agrees to pay out the reward after Khurana informs him about the anonymous telephone call. Meanwhile, Ravi also sends an anonymous letter at Rane's office, instructing him to open the letter and follow its instructions only after Surendra's killer has been sentenced by the court. He also plants circumstantial evidence (his burnt shirt, cigarette butts, pieces of rope and an iron rod with his fingerprints) to prove that Ravi kidnapped Surendra, brought him to an isolated place and then killed him with an iron rod. Acting upon the received information, Khurana and Kulkarni recover the evidence and arrest Ravi, who confesses in the court that he kidnapped Surendra for the ransom of ₹5 lakhs, tied him up at the isolated place and when Surendra tried to escape, he accidentally killed him and threw his dead body off in the gutter. As a result, Ravi is sentenced to death by the court, devastating his family, Neela and her father. While Ravi's mother and Neela attempt to make some sense out of Ravi's confession, also unsuccessfully beg for clemency from Narendra, Ravi suffers from another headache episode in prison and is rushed by Khurana and Kulkarni to the hospital, where, serendipitously, it is Dr. Shah who examines him. Aware of Ravi's medical history, Dr. Shah wastes no time in getting him into the operation theatre, and Ravi miraculously undergoes a successful brain surgery with no side-effects, but it is too late now as Ravi is a convicted criminal for kidnapping, ransom and murder, which he planted on himself.
Two months later, Ravi summons Neela and Rane for a meeting at the hospital and admits being innocent, but Rane states that now there is no way out and that he will need fresh evidence to reopen the case. In an attempt to save himself from execution, Ravi escapes from the hospital in search of the real murderer of Surendra, and is aided by Neela in his pursuit. The two escape to a hotel for safety, where Ravi meets a man named Mahipat Rai (Madan Puri), who has a girlfriend despite being married to a millionaire wife, Sulakshana (Lalita Kumari). Ravi notices that Mahipat is shockingly wearing the same ring that he had noticed on Surendra's finger. After being questioned by Ravi, Mahipat reveals that the ring was sold to him by a curio shop owner named Prakash (Mac Mohan). With the help of Prakash, Ravi traces the origin of the ring to Michael D'Souza (Pran), a kind-hearted and happy-go-lucky professional thief, whom Prakash had purchased the ring from. Ravi meets Michael and confronts him over Surendra's ring, when Michael admits to stealing the ring and claims to be the sole witness to Surendra's murder. On that rainy night, Michael had stopped a car with a driver and another man sleeping on the backseat, and had threatened the driver at gunpoint. The driver claimed that the sleeping man is his sick friend and he is taking him to the hospital. Since he had nothing to give, the driver removed the ring from the sleeping man's finger and handed it over to Michael. Ravi understands that the sleeping man was Surendra and was already dead, and that the driver was his murderer. In exchange for tracking down Surendra's real murderer, Ravi offers Michael the reward of ₹5 lakhs as well as Surendra's ring.
However, Prakash advises Michael to betray Ravi and go to make a deal with Narendra, who will give him ₹5 lakhs for the information on the murderer. Michael visits Surendra's house to meet Narendra for the same, but is shocked to identify Narendra as the driver of the car, whom he had stolen Surendra's ring from. Seeing no other way out, Narendra admits that Surendra's wife, Mona (Ashoo), had an extramarital affair with him, which Surendra discovered on the rainy night and banished Narendra from the house. He also alleged that Narendra is his adopted brother, but a furious Narendra immediately retaliated by smashing glass bottles on Surendra's head, killing him instantly due to head injuries. Narendra then threw Surendra's dead body off in the gutter, faked his kidnapping and ransom, and announced the reward of ₹5 lakhs to cover up his crime. After learning this, Michael agrees to hand over Ravi to Narendra in exchange for ₹7.5 lakhs. Michael instructs both Ravi and Narendra to reach an isolated cabin at the same time, where Ravi will find Surendra's real killer, and Narendra will find Ravi. Michael is now perplexed as he is aware that Ravi never murdered Surendra, and yet he admitted to the crime in the court.
In an attempt to find out the truth about Ravi's strange actions, Michael visits Ravi's house to realise that Ravi took the blame of the murder just to provide for his family, and takes an oath that Ravi will return home to them. Later, Michael meets Narendra at the place where he had summoned him and Ravi. When Ravi and Neela arrive there, they are horrified to witness Narendra shooting three bullets in the stomach of Michael, already aware that he will expose the truth about his crime. At this point, Ravi learns that the murderer of Surendra is none other than Narendra, Surendra's own brother. He drives away desperately to bring a doctor back in time, while a gravely injured Michael holds Narendra at gunpoint along with Neela during the time. As Ravi is returning with a doctor, Kulkarni and the police discover his car and pursue Ravi to the crime scene. As Michael's health deteriorates, Narendra attempts to escape, but Ravi appears on time and captures him. Michael provides his testimony to Kulkarni about Ravi's innocence and Narendra being Surendra's killer, and eventually dies in Ravi's arms. As a result, Kulkarni and the police arrest Narendra for both Surendra and Michael's murders, and acquitt Ravi from the charge of Surendra's murder. The film ends with the funeral of Michael when his oath of reuniting Ravi with his family is recalled.
