Mrityudaata is a story about Dr. Ram Prasad Ghayal (Amitabh), a surgeon whose scalpel is like a magic wand. He is married to Janaki (Dimple) and has a brother named Bharat. Bharat is in love with a dancing doll named Renu (Karishma), who is also loved by the baddie's brother (Deepak Tijouri).
Bharat, an architect, refuses to sign a power project that involves heavy kickbacks and displacement. He is falsely implicated in a plot and sent to jail. Unable to bear the humiliation, he commits suicide, and Renu ends up marrying Deepak instead of mourning her beloved's loss.
Now, it is time for our Mrityudaata to avenge the loss of his wife and brother. He trades his scalpel for a machine gun and his apron for a commando coat and cap.