Plot

Codename 13, a 17-year-old assassin, is suspended due to a sloppy mission in Japan. She meets 11-year-old Monji, who loses his mother, and sets out to rescue him.

Codename 13, a 17-year-old trained assassin is under suspension because of a sloppy mission in Japan. The girl built a conscience when she met Monji, an 11 year old boy who lost his mother to a crime syndicate. When Monji is captured, 13 is hellbent on setting a path of destruction to rescue the boy, including going against her mentor and the organization who hires her, the Shadow.

Codename 13 (Aurora Ribero), a 17-year-old trained assassin known as a Shadow, is part of an international organization of assassins. On a mission in Japan, she assassinates her primary target Yoshinori, the leader of a criminal clan. However, 13 is dazed after accidentally killing a bystander (the Geisha (Naomi Hitanayri Christy) who had been summoned by the clan head) and is incapacitated. Umbra (Hana Malasan), 13's mentor, eliminates the rest of the clan and rescues her. Umbra reprimands 13 for her lapse in focus and puts 13 under suspension, for a psych retraining, in Jakarta. 13 considers herself as more than just a number but gets severe headache when she tries to remember her name. She is given medication to control her headache, indicating that she has been conditioned to forget her past. Umbra herself is tasked to undertake a mission in Cambodia by the Handler (Chew Kin Wah).

During suspension, 13 has recurring nightmares of her mother's death and routinely contacts her handler who instructs her to consume her medication and wait. 13 encounters 11-year-old Monji (Ali Fikri) and his mother, Asti, who live next to 13's safe-house. Asti works as an escort for Haga (Agra Piliang), a human trafficker and owner of the club Moonrose. One night, 13 witnesses Haga and his men assaulting Monji and his mother but does not intervene. The following morning, Monji's mother is found dead due to an overdose and Monji is warned by police detective Prasetyo (Adipati Dolken).

Receiving no instructions for over two weeks, 13 becomes restless and stops taking the medication prescribed to her. She later befriends Monji who wishes to avenge his mother. 13 takes Monji to Asti's grave to comfort him. The following day, 13 discovers that Monji has gone missing, and she forces Jeki (Kristo Immanuel), a foot soldier for Haga (who had come to Asti's apartment to remove evidence of Haga's involvement), to take her to Haga, believing Haga had kidnapped Monji.

Jeki begrudgingly takes 13 to the Moonrose. Jeki explains that Haga and his twin sister Soriah (Taskya Namya) are a part of a crime syndicate that involves the corrupt Prasetyo who is also Haga's lover. The syndicate also includes Ariel (Andri Mashadi), a drug lord running as vice governor of Jakarta alongside his father, Soemitro, an influential criminal kingpin.

At the Moonrose Soriah arranges a drug deal with drug lord Abi Kabil. Jeki requests an audience with Haga to Soriah, presenting 13 as a gift for his boss. 13 looks at the CCTV footage from the club and learns that Monji had come to the Moonrose the previous night and was kidnapped by Prasetyo and Haga.

In Cambodia, Umbra eliminates a number of her masked targets and rendezvouses with a fellow Shadow, Troika (Daniel Ekaputra), who was also assigned the mission unbeknownst to Umbra. Troika points out that the people Umbra has been killing were also Shadows. Umbra tracks down her main target, Volver (Eva Celia), a Shadow. Umbra bests Volver but hesitates in killing her upon learning that Volver is pregnant, which is thought to be impossible for Shadows. Volver asks Umbra to join her, but Umbra just lets her escape. However, Troika finds Volver and kills her.

13 kills Haga, which enraged Soriah who shoots up the Moonrose and inadvertently draws the police's attention. 13 kills the Moonrose's security team and eventually escapes with Jeki but the two part ways after the latter's refusal to help in 13's mission to recover Monji.

Prasetyo desperately hunts down 13 after hearing of Haga's death from Ariel and Soriah takes shelter with Ariel. Soemitro berates Ariel for needlessly causing chaos by killing Asti who was pregnant with Ariel's child. Soemitro says that Ariel should have taken Asti to an abortion clinic rather than brutally killing her. In turn, Ariel tortures the captive Monji.

Later that night, Prasetyo and his corrupt police squad stormed Jeki's grandmother's house but their attack was thwarted by 13. Prasetyo escapes (with help from Jeki who wanted to save his grandmother's life) and leads 13 into a trap at Ariel's mansion. Before she is incapacitated, 13 kills Prasetyo. Ariel and Soriah were determined to torture and kill 13 as revenge but the two are stopped by Soemitro. Soemitro intends to use 13 as protection during the Kabil drug deal as the syndicate has lost many members because of 13 (13 can help wipe out Kabil's entire army). Soemitro argues that the deal with Kabil is worth $ 2 million, and he needs the money for his campaign. 13 spends the night with Monji who apologizes for being unable to let go of his mother.

After the mission in Cambodia, The Handler reprimands Umbra for hesitating in killing Volver to which Umbra complaints that she was not informed that the targets were also Shadows. The Handler replies by informing Umbra of 13's killing spree, tasking Umbra and Troika to neutralize her to prevent further damage.

Before the deal, Ariel tasks 13 to kill Kabil once the exchange has taken place. As the deal happens, Monji-who is in the same car as Soemitro and Jeki-succumbs to his injuries and dies. Realizing this, Jeki alerts 13, who becomes dazed and does not kill Kabil. Jeki takes control of the car he's in and drives it into Kabil's men.

In the ensuing chaos, Kabil orders his men to open fire on Ariel's, leading to a gigantic shootout that killed Soemitro, Kabil, and all of Kabil's men. 13 takes advantage of the confusion in the aftermath of the shootout to kill off Ariel's men, and after a prolonged fight, eventually eliminates Ariel. However, 13 is cornered by Soriah, who is swiftly killed by Jeki. 13 retrieves Monji's body and leaves with Jeki. During the way back from the shootout, Umbra and Troika crashes into 13 and Jeki's car, incapacitating the two.

The Handler tasks Umbra to execute 13 but Umbra hesitates once again, this allows Jeki to overpower her before he is killed by the Handler. 13 escapes her restraints and runs into a nearby building where she is pursued by Troika. 13 kills Troika just as Umbra arrives. 13 and Umbra duels each other, and Umbra wins despite suffering heavy wounds. The Handler arrives and orders Umbra to kill 13, Umbra disobeys and attacks the Handler. Umbra is fatally shot which leads to 13 killing the Handler. 13 cradles the dying Umbra and Umbra reveals 13's true name, Nomi, to 13 as Umbra dies.

Returning to Jakarta, 13 buries Monji but discovers that other Shadows are coming after her. The Shadows are led by 14 (Mawar Eva De Jongh), 13's successor, who wants to kill 13. A masked man arrives and kills two of the Shadows and threatens 14 before she leaves. The Masked Man reveals himself to be Master Burai (Yayan Ruhian), Umbra's revered mentor, who requests 13 to become his Mentee. 13 agrees and asks that she be called Nomi from now on.