Dr Ram Prasad Ghayal (Amitabh Bachchan) is a renowned doctor who has been successful in all the operations in his career and has skillfully operated many delicate surgeries. He lives with his wife Janki (Dimple Kapadia) and brother Bharat (Arbaaz Ali Khan). Bharat is in love with Renu (Karishma Kapoor), the daughter of Umeshchan Jain (Tiku Talsania). At the same time, Raja Tunga (Deepak Tijori), the brother of Rana Tunga (Mukesh Rishi) has a longing for Renu. The miscreant Raja with his mob severely assaults Bharat when Bharat resists Raja's advances towards Renu.

A corrupt minister Mohanlal (Ashish Vidyarthi) wants to execute a disastrous scheme called "Pawanghat Power Project" at the expense of the lives and property of the tribes living at the project site. He coaxes and later threatens Bharat, the concerned engineer to sign his approval for the project, whereas Bharat refuses to endorse such a scheme. On the other hand, Rana devises an evil plot against Bharat to wipe the latter out eventually leading to his brother Raja winning Renu. Bharat is framed for murdering a woman and Inspector Danapani (Mushtaq Khan), a subordinate of Rana, arrests him and puts him behind bars. Woefully, Bharat dies in jail presumably by committing suicide. The agony of Bharat's death claims the life of Janki as well. With the death of his beloved wife and brother, Dr Ram becomes desolate and alcoholic. Renu marries Raja, without any regret for the death of her former lover.

Now that Bharat is dead, Mohanlal conspires with Rana for the implementation of the power project. However, they end up becoming enemies of each other. Mohanlal plans to kill Raja. His henchmen attack Raja who is critically injured. Raja is admitted to hospital where Dr Ram is to conduct his operation. Renu fears that Dr Ram may kill Raja to take vengeance for the death of his brother. She refuses to sign the operation papers, but Dr Ram, who considers it his moral duty to save the life of a patient regardless of them being his friend or foe, conducts the operation. His expertise pays off as Raja is saved. He goes out to convey the news to Renu, but returns to find Raja dead, beyond all his expectations. Renu files an F.I.R. against Dr Ram, who is arrested and imprisoned.

In jail, Dr Ram meets an inmate bearing the number 92, Prof Nizamuddin Azad (Pran), a scientist of "Bharat Atomic Energy". He has been jailed after a false allegation of revealing confidential nuclear formulae to foreign nations. He tells Dr Ram that his brother Bharat did not commit suicide, but was tortured to death by Insp. Danapani, which he witnessed. Dr Ram now realises that his past misfortune was a result of the evil motives of some antagonists of the nation. He becomes the Angel of Death (Mrityudaata), who will put all those malefactors to death.

Dr Ram breaks away from jail and nabs Insp. Danapani who says that Mohanlal planned the murder of Bharat using his influence over police. He also says that Raja was killed by Dr Siddiqui (Avtar Gill) by cutting off the oxygen supply after Mohanlal bribed him to kill Raja. Dr Ram kicks Danapani off the building to his death.

Meanwhile, Mohanlal has allied with another influential politician, Trilochan Tripathi, a.k.a. TT or Terror of Terrors (Paresh Rawal), who keeps up an honest appearance among the masses, but works for his own interests at the cost of the welfare of the public. Dr Ram corners Dr Siddiqui at the roof of Umeshchan Jain's house, who confesses to killing Raja, and accepting a bribe from Mohanlal. Dr Ram captures a video of Dr Siddiqui's revelation before putting him to death. Soon, Dr Ram kills Mohanlal.

One day, Trilochan Tripathi addresses a gathering when Dr Ram publicly puts a video on view in which Tripathi signs an agreement with a foreign syndicate related to "Pawanghat Power Project". Later, Tripathi would fool the public with false promises of power distribution. The enraged crowd chases Tripathi through the streets when Rana arrives for his rescue. Rana fires at Dr Ram who burns Rana and Tripathi to death.

The movie ends after Dr Ram succumbs to his injuries.

Mrityudata's premier show was held in Jaipur, Rajasthan, India in the month of April, 1997. Live coverage was organised by Star Plus Channel which was advertised locally by VComm, Jaipur headed by Mr. Sandeep Prabhakar. This was the first and last premier of any Bollywood movie held in Jaipur till date (April, 2018). This event was organised in Raj Mandir (one of the most unique movie theatres in India and Pinkcity).

• Amitabh Bachchan as Dr. Ram Prasad Ghayal
• Dimple Kapadia as Mrs. Janki Ghayal
• Karishma Kapoor as Renuka Jain
• Arbaaz Ali Khan as Bharat Prasad Ghayal
• Paresh Rawal as Trilochan Tripathi (T.T.) / Terror of Terrors
• Mukesh Rishi as Rana Tonga
• Ashish Vidyarthi as Mohanlal
• Tiku Talsania as Umeshchan Jain
• Mushtaq Khan as Police Inspector Danapani
• Deepak Tijori as Raja Tonga
• Aashif Sheikh as Aasif Shaikh
• Farida Jalal as Mrs. Ghayal
• Pran as Professor Nizamuddin Azad / Prisoner #92
• Daler Mehndi as himself (Special appearance in song "Na Na Na Na Re")

3 million audio cassettes were sold. The soundtrack was a successful release for ABCL.