Sancaka is the lightning-fearing son of a factory worker in Indonesia. He joins a strike led by his fellow workers, and when the crowd clashes with security, his father is stabbed by a coworker and dies. In his grief, Sancaka discovers a surge of electricity within him, unleashing bolts that crackle from his body. A year later, his mother leaves for another city to find work and never returns. He becomes homeless in Jakarta, where he befriends a street kid named Awang who teaches him basic self-defense. They plan to freighthop and ride a train toward a safe haven in Tenggara, but only Awang makes the leap onto the moving train. Now an adult, Sancaka works as a guard and a mechanic at a newspaper printing factory.
Within Indonesia's political underworld, a crime boss named Pengkor controls most assembly members and commands a nationwide army of orphans trained as assassins. Pengkor plots to poison rice supplies with a drug that dulls the moral sense of fetuses after birth, aiming to recruit a new generation of followers. Many people demand that the government release an antidote, and legislator Ridwan Bahri leads his colleagues in backing distribution while Pengkor's allies oppose it.
One day, Wulan helps her neighbor fend off harassing thugs. In a second confrontation, Sancaka is struck by lightning and reawakens his powers. With Wulan's help, her little brother Teddy and Sancaka's fellow guard Agung, he learns to control his abilities and even crafts a homemade costume. He begins fighting the thugs, including the violinist Adi Sulaiman, one of Pengkor's orphan agents.
The legislature passes the antidote distribution bill, but Ridwan Bahri soon discovers that the so-called “drug” in the rice is harmless; rather, the antidote is the true delivery method, and the manufacturer is a shell company controlled by Pengkor. Ridwan tells Sancaka to stop distribution, prompting Pengkor and his team to seize [Agung], [Wulan], and [Teddy]. Sancaka unleashes his powers to repel most attackers, though Agung dies in the fight. Ridwan then shoots Pengkor. Sancaka catches up with the distribution convoy and halts it, aided by [Sri Asih]. He then uses his powers to destroy all bottles containing the antidote.
At a museum, Pengkor's partner Ghazul breaks open a wall, revealing Ki Wilawuk's buried tomb. Ghazul uses a sample of Sancaka's blood to reattach the body within Ki Wilawuk, resurrecting the powerful medieval warrior. Ghazul informs Ki Wilawuk of Gundala’s arrival, and Ki Wilawuk orders him to gather his army for revenge.
