A wealthy, but evil man named Zafar Khan (Kader Khan), has fallen in love with a girl named Salma (Waheeda Rahman) and wants to marry her, but she and her father do not let him. Zafar is arrested for various crimes and is imprisoned for 10 years, but when he is discharged, he sees that Salma is married to a good man named Aslam Khan (Satyendra Kapoor). Zafar Khan, wants to convince Salma to marry him but Salma refuses.
Zafar plots his revenge by flooding the region in which Salma lives in, killing her father, injuring Aslam and Salma, causing her to lose her memory. During this catastrophe, Salma is also separated from her young son, Iqbal (Amitabh Bachchan).
Zafar abducts Salma and tells the world she is his wife. He also adopts an infant from an orphanage in Kanpur, a boy named Sunny (Rishi Kapoor), for Salma to raise on the advice of a psychiatrist. Meanwhile, Iqbal is reunited with his uncle, who has lost his wife and son in the flood. The uncle will raise Iqbal as his own, as they have no more family.
Years pass, and Iqbal and his uncle work as coolies. Iqbal has grown up to a be a dashing, confident young man, and is considered the leader of the local coolies. He organizes a labor strike, which brings the station to its knees. Sunny, a young, budding reporter, is covering the story. While speaking to Sunny, Iqbal sees a picture of Sunny's mother who turns out to be Salma.
Iqbal rushes to Salma's house to see her after all these years, but upon meeting her son, she has no recollection of him. Zafar is infuriated by Iqbal's trespass and has his guards severely beat him, while he takes Salma to the psychiatrist to administer electric shocks on her so that her memory never returns.
Iqbal and Sunny become friends, and both find love; Iqbal with a Christian girl Julie D'Costa (Rati Agnihotri) and Sunny with his childhood sweetheart, Deepa (Shoma Anand). Things are looking up, but the coolies uncover a banking and housing scandal against them.
After a series of run-ins with the corrupt parties, Iqbal finds himself in a fight to the death with Zafar. Salma returns at a very pivotal scene in the film, during the election standoff between the communist workers under Iqbal and the capitalist lords under Zafar with her old memories intact and she publicly testifies against Zafar and how he destroyed her family. In the crowd is an old man, who turns out to be Iqbal's long-lost father Aslam.
Also, Iqbal's uncle recognizes a birthmark on Sunny, proving that Sunny was indeed the son he thought he had lost in the great flood. The family is reunited, much to the fury of Zafar, who then proceeds to shoot Iqbal's beloved mamu (uncle) who cared for him in his youth. Iqbal and Sunny both chase after the evildoers, killing Mr. Puri and Vicky in the process, until Iqbal corners Zafar in a masjid.
The holy shroud from the shrine flies onto Iqbal's chest, and Iqbal defiantly faces Zafar with the belief in God's protection from harm with His name on his chest. He is shot several times by Zafar, but he continues to chase Zafar up the minaret, saying a part of the shahada with each shot. With the last of his strength, he cries the takbir and pushes Zafar off the parapet, killing him instantly, and Iqbal collapses into his mother's arms. Coolies from all faiths pray hard for his recovery, and Iqbal recovers from his injuries.