In a non-linear, time-shifting narrative, the film moves between the present in London and the past when Udham Singh was part of the Hindustan Socialist Republican Association, and it delves into the motives behind his decision to shoot the Irish-born officer in the Indian Civil Service, Michael O'Dwyer. Udham (often known as Sher Singh) is revealed as someone who has just left prison in Punjab under British rule and remains under constant watch by the colonial authorities. He travels from India to the USSR during what looks like winter, and from there makes his way to London by ship, managing to stay out of sight of the authorities while earning a living as a salesman and later taking up work as a welder.
The story takes us to a pivotal moment in Caxton Hall, where Udham moves through the crowd as General Reginald Dyer delivers a speech about his role as Lt. Governor of Punjab and his suppression of a major uprising. Udham confronts the mood of the crowd and approaches O'Dwyer, ultimately shooting him and being taken into custody. In custody, Udham is assigned a lawyer who begins to coax out his backstory. Although the court delivers a death sentence, Udham delivers an impassioned speech that denounces British rule in India and reaffirms his commitment to the Indian freedom movement. He protests the conditions of his detention, undertakes a 42‑day fast that is forcibly ended by feeding, and gradually opens up to the investigating inspector about the reasons behind his act. He earns the reverent title of Shaheed-E-Azam through these experiences.
A flashback reveals Udham in 1919 as a young adult working in a textile mill near Amritsar, where he shares a life with a mute girlfriend. On 13 April 1919, under Colonel Dyer's orders, Gurkhas, Baluchis, and sepoys are directed to fire on a peaceful crowd of about 20,000 at Jallianwala Bagh. Udham sleeps, only to be awakened by the chaos as his friends and countless others are wounded or killed. He races to the grounds to help, and along with a handful of volunteers, he assists survivors and ferries the injured to a makeshift hospital that rapidly becomes overwhelmed. In his later life, he is shown holding a photograph of his idol, Bhagat Singh, captured during Bhagat Singh’s imprisonment in his final days.
Following India’s independence, Udham’s ashes are brought home at the request of Punjab’s Chief Minister and are immersed in the Sutlej River—the same place revered by his idol. The film ends by returning to the Hunter Commission setting, where the two men from the past—Dyer and O'Dwyer—offer their own accounts to history, closing a circle that weighs the costs and consequences of colonial rule and the pursuit of justice.
