KAASHI is the story of a young man who burns dead bodies for a living. Kaashi (Sharman Joshi) lives in Varanasi and burns dead bodies to make a living. This is his family profession. He lives with his father (Kamalakant Mishra), mother (Anita Sehgal) and younger sister, Ganga (Priyanka Singh). He meets Devina (Aishwarya Devan), a journalist, who has come to Varanasi. Devina is introduced to Kaashi's family as she wants to write about him. Devina and Kaashi soon fall in love with one another.
One day, Ganga doesn't return from college till night. A worried Kaashi and Devina launch a search for Ganga but draw a blank. Then Devina introduces Shruti (Mugdha Meharia) to Kaashi. Shruti, a friend of Ganga, tells Kaashi that his sister was in a relationship with Abhimanyu Pandey (Mehul Surana), son of influential politician Balwant Pandey (Govind Namdeo). Shruti also tells Kaashi that Ganga had been very disturbed of late because she was pregnant with Abhimanyu's child.
Convinced that Abhimanyu must be the reason for Ganga's disappearance, Kaashi swears revenge against Abhimanyu. In the heat of a moment, he ends up killing Abhimanyu. But he pleads innocence in court after his arrest for the murder of Abhimanyu. Before Kaashi is arrested, he learns that Ganga is dead. He performs the last rites of Ganga before being arrested by the police. What happens thereafter? Is Ganga really dead? Who killed her? Why does Kaashi plead innocent in court?