Sancaka Abimana Aryasatya is the astraphobic son of an Indonesian factory worker. As he helps lead a factory strike, violence erupts when angry workers clash with security guards, and his father is fatally stabbed by a fellow worker. In his despair, Sancaka unleashes lightning bolts from his own body. A year later, his mother leaves for another city to find work and never returns. He becomes homeless in Jakarta, where he befriends Awang, a fellow street child who teaches him self-defense. They dream of freighthopping to a safe haven in Tenggara, but only Awang manages to hop onto the train. Now an adult, Sancaka works as a guard and a mechanic in a newspaper printing factory.
Most of Indonesia's assembly members are controlled by Pengkor Bront Palarae, a crime boss who commands a nationwide army of orphans raised as assassins. Pengkor plots to poison rice supplies with a drug that supposedly inhibits a fetus’s ability to distinguish right from wrong after birth, hoping to birth a new generation of followers. The public demands an antidote, and legislator Ridwan Bahri Lukman Sardi leads the charge to distribute it; Pengkor’s allies oppose the move.
One day, Sancaka helps his neighbor Wulan fend off harassing thugs. In a second fight, he is struck by lightning again, reawakening his latent powers. With Wulan’s support, her little brother Teddy, and Sancaka’s fellow guard Agung Pritt Timothy, he discovers and learns to control his abilities, even crafting a homemade costume. He then begins to battle the thugs, including Adi Sulaiman, one of Pengkor’s orphan agents.
The legislature approves the antidote distribution, but Ridwan quickly uncovers a darker truth: the supposed “drug” in the rice is harmless, and the antidote is the real delivery mechanism. The manufacturer operates under a shell company controlled by Pengkor. Ridwan urges Sancaka to stop the distribution; Pengkor’s team seizes Agung, Wulan, and Teddy. Sancaka unleashes his powers, fending off most attackers, but Agung dies in the chaos. Ridwan shoots Pengkor, and Sancaka catches up with the distribution convoy, aided by Sri Asih. He uses his powers to destroy every bottle of antidote.
Back at a museum, Ghazul Ario Bayu reveals a buried ancient tomb. After secretly extracting some of Sancaka’s blood, Ghazul uses it to reattach a body to a head, reviving Ki Wilawuk, a powerful medieval warrior. Ghazul informs him of Sancaka’s arrival, calling him “Gundala”—the ancient Javanese word for “Thunder”—and Ki Wilawuk orders him to gather an army to seek revenge.
