Aag Hi Aag is an action drama. The movie follows the story of an Army officer Bahadur Singh (Dharmendra), who is married to Ganga (Moushumi Chatterjee) and has a young son Vijay. Bahadur’s sister get raped and killed, when Bahadur tries to get justice, he is shunned by a corrupt police officer. Later, he decides to take the law in his hands and joins the gang of a bandit, Daulat Singh (Danny Denzongpa). He then kills an innocent doctor, Raghuveer Singh (Vinod Mehra), assuming him to be a policeman. Later, he repents his actions and surrenders himself. Years later, Vijay (Chunky Pandey) is all grown up, and doesn’t know much about his father. Raghuveer's son Suraj (Shatrughan Sinha) becomes ACP and is all set to exact revenge from his father’s killer. How the lives of different characters change with the unexpected twists forms the rest of the plot.