The plot is an intricately woven one. It starts from childhood with the story of Ashok (also called Shoki by his childhood friend Vinod) (Dharmendra) who is a wealthy industrialist's only son. He is passionate about cars from childhood. He befriends Vinod (Vinod Khanna) who is passionate about trains; its his dream to make India's fastest train. Rakesh (Vinod Mehra) shares same passion as Vinod. Randhir (Danny Denzongpa) is in a tussle from childhood to make a better train than Vinod's. Childhood turns into adulthood and one day both attend a dance function organized by the Indian Railways. This is where Ashok and Vinod fall in love with two beautiful women: Seema (Hema Malini) and Sheetal (Parveen Babi). Ashok is now deeply in love with Seema and they are planning to get married after their engagement. Vinod is married to Sheetal and they have a son Raju. One day Vinod, who is now a top notch railway engineer, gets awarded with the contract to build a super-fast express train between New Delhi and Mumbai. Rakesh (Vinod Mehra) is his assistant. Randhir, the losing engineer and ex-lover of Sheetal, swears revenge and leaves.
As the three friends celebrate Vinod's success, Seema leaves for a pilgrimage. Ashok hears that his father has died. He rushes to his funeral and finds out that his father was debt-ridden, and he is left with nothing. As he is still recovering, he gets a letter from Seema breaking off their relationship stating that she was interested in him as a rich man and, since he is now poor, she is not interested anymore. Heartbroken, Ashok leaves town.
Six years pass by. Vinod has completely focused on building the train, ignoring his wife and son. On the day of the train's inauguration, she comes to fetch him for their anniversary party. He refuses to go since the next day is the train's inaugural journey. Heartbroken, she puts her son, Raju, on the train to go to her mother, and leaves Vinod. Iftekhar, their boss, asks Vinod to go to Mumbai by flight for the arrival of the train. Vinod refuses saying that he needs to be in the control room. So his assistant and friend Rakesh goes instead.
The train starts from New Delhi where a lot of the characters board. Rajendra Nath is a devout Hindu priest. Om Shivpuri is a royal king, Raja Mam Mohan, traveling with his wife Padmini. Ranjeet is a smuggler fleeing with stolen diamonds and his girlfriend Raziya. Sujeet Kumar is an undercover police officer dressed as a Christian priest and following Ranjeet the smuggler. Asrani is an ex-Army colonel P.K. Bhandari. Keshto Mukherjee and Paintal are traveling without tickets hiding in the train's lavatories. Simi Garewal is a school teacher, taking a group of students on a visit to Mumbai. Neetu Singh is fleeing her home to escape a forced marriage. Ravi (Jeetendra) is a small-time thief who tries to befriend Neetu Singh to steal her jewellery. Seema is traveling to Mumbai with her cousin (Navin Nischol) who is a doctor. Rakesh's pregnant wife is traveling to Mumbai with her mother. Ashok also quietly boards the train so that he can be a part of his friend Vinod's success and is shocked to see Seema. He sees her with her cousin and mistakes him for her husband. He snaps at her before she can say anything, but befriends Raju after recognizing him.
Unknown to all of them, Randhir has put a bomb in the engine at the Mathura Railway station and disengaged the vacuum brakes so that even guard wouldn't be able to stop the train. The bomb was timed to explode halfway through the journey. He hopes to sabotage the train and thereby destroy Vinod's reputation without a scant thought to the lives of the passengers. Meanwhile Ashok leaves the train as he does not wanted to travel with Seema in the train. He meets Randhir in a bar where Randhir tells him that he has fulfilled his and Ashok's revenge. (He was misunderstood that Ashok must be seeking revenge from Seema for her betrayal). Knowing this Ashok immediately leaves to catch the train before explosion time so that he can save his friend's train and save passengers. He manages to catch the train at Kota Railway station but is too late.
Halfway, the bomb explodes killing the drivers Jeevan Lal and Dango and destroying the brakes and accelerator. Ashok goes outside the train and goes to the engine compartment and saves the guard (Osman Ali) and brings him back. Vinod, who is desperately trying to save their lives, talks to them through All India Radio and asks them to go to the engine compartment and apply the emergency brakes.
The radio broadcast completely panics all passengers and the train cooks come running to find out what has happened. In their haste, they leave the cooking gas on. The news also panics the relatives who are waiting at Mumbai and they besiege Vinod. Sheetal also comes to him and shouts at him asking him to save their son, Raju.
Ashok, Ravi and the guard climb on top of the train and try to reach the engine. Meanwhile, Rakesh's wife enters labor and Seema's doctor cousin attends to her, asking for some hot water. A cook lights a match to heat up some water in the kitchen. The open gas explodes killing the guard Osman Ali, the cook and several passengers and half the train starts burning. Ashok and Ravi barely make it back and with the help of some passengers put up some gaps between the burning compartments and the passengers.
Vinod tries another effort by sending a helicopter and trying to get someone to land on the engine compartment. Randhir sabotages this mission by volunteering to go on the helicopter. He drops on to the engine compartment but does nothing, leading Ashok and his superiors to believe he is dead.
Meanwhile Ashok finds out why Seema left him. She had lost her leg on the way back from the pilgrimage. She didn't want to be a burden on him in his poverty and decided to go away. They patch up. Ravi and Neetu also fall in love. Sheetal also comes back to Vinod and apologizes for her behavior. She gives him courage for his last attempt to save the train.
Rakesh, who is in Mumbai, tries to build a steep incline quickly which will reduce the speed of the train once it reaches Mumbai and may yet stop the train but he is running out of time as the train is speeding towards Mumbai and is just hours from reaching it.
Vinod tries one last effort by getting an engine to drive along the Super fast train. He asks Ashok and Ravi to come up top and throws a rope saying that he will come over to the train and stop the train himself. Ranjeet tries to escape by using the same rope to the other train knowing that he will be arrested in Mumbai. Asrani tries to stop but Ranjeet throws him off the train. Ashok fights Ranjeet who falls off the train. Vinod comes over to the train.
He says that he has brought fireproof suits and some dynamite (just in case). They will wear the suits, go to the engine, and apply the emergency brakes. Vinod, Ashok and Ravi go through the fire to the engine where they find Randhir. Randhir tries to kill Vinod but falls off the train in the scuffle.
They reach the engine to find that the drivers are dead and all systems have failed. Ashok comes up with an idea of blasting the couplings of the compartments from the engine. Vinod disagrees saying that passenger compartments will derail if blasted off at this speed, but then remembers the incline being built by Rakesh. They send Ravi back to warn the passengers and to ask everyone to tie themselves to their seat.
Vinod asks Rakesh over wireless to clear the incline area even though it isn't completely ready. Ashok and he set up the dynamite charges on the couplings. As the train starts climbing, they blast the dynamite and jump off the slowing engine. The engine blasts through Mumbai station and stops on the road. But the passenger compartment slows down and comes to a complete halt. All passengers get off safely. Vinod and Ashok happily come walking they're hurt but alive.
Everyone connects with their relatives and the film ends as a tribute to the soul of India. Some of the film scenes were shot in Delhi, for example, at Lodhi Garden. Some of the highights of the movie are the is fast car driving by Dharmendra and the comical scene at Lodhi Garden.
