Indonesian special tactics officer Rama, portrayed by Iko Uwais, begins his journey with a heartfelt farewell to his father and his pregnant wife, promising to "bring him home." He joins a specialized 20-man police unit, including officers like Bowo (played by Tegar Satrya), Dagu (Eka "Piranha" Rahmadia), Sergeant Jaka (played by Joe Taslim), and Lieutenant Wahyu (portrayed by Pierre Gruno). Their mission targets crime lord Tama Riyadi (depicted by Ray Sahetapy), who controls an apartment building in the slums of Jakarta, allowing criminals to dwell there in exchange for protection.
Under the cover of darkness, the team successfully infiltrates the building and disarms various criminal occupants. However, their stealth is short-lived when a young lookout spots them and signals others. As chaos ensues, Tama's henchmen retaliate, resulting in the deaths of many officers and leaving the remaining police trapped. In a shocking twist, Wahyu reveals that the mission was a setup, crafted in collusion with corrupt police officials, aiming to eliminate Tama. They are officially cut off from any backup, making their situation increasingly dire.
Amid the turmoil, the few surviving officers scramble to find refuge. Officer Bowo suffers an injury, escalating the tension as Rama utilizes his skills to craft a makeshift explosive, dispatching their pursuers temporarily. The remaining members split into two teams, with Rama and Bowo seeking shelter in apartment 726. There, they plead with the hesitant tenant to hide them, making it clear the stakes are life or death. Just as they take cover, a group of armed thugs invades the apartment but fails to discover them.
Rama takes charge, tending to Bowo's injuries, while a fresh wave of threats compels him into the fray again. He faces a machete-wielding gang, taking down their leader with sheer ferocity before making a daring leap through a window. His path soon leads him to a chilling reunion with Andi (played by Doni Alamsyah), revealed to be his estranged brother. Their family ties are tested as Rama implores Andi to abandon his life of crime and reunite with their family, but Andi is resolute in his choices.
Meanwhile, Jaka and his allies confront the formidable Mad Dog (portrayed by Yayan Ruhian). This fierce exchange culminates in an intense showdown, with Jaka tragically falling at the merciless hands of Mad Dog. In a cunning maneuver, Mad Dog later captures Andi, leading to his betrayal.
In this relentless battle, Rama continues to push toward Tama, engaging in fierce combat with Mad Dog after rescuing his brother. The duo demonstrates their sharpened skills and unity, ultimately defeating their adversary, but not without significant struggle. Meanwhile, Wahyu's betrayal cuts deep, as he kills Dagu before facing off against Tama himself. The web of deception for Wahyu grows, leaving him to contemplate his fate in despair.
With the siege drawing to a close, Andi leverages his connection with the tenants to facilitate a precarious escape for Rama and his injured companions. He gifts Rama vital information and recordings that could expose the corruption within the police force. As they part ways, Andi chooses his criminal life over a return home, leaving Rama to ponder their fractured bond amidst the chilling events they've endured. He exits with Wahyu and a wounded Bowo, facing an uncertain future, while Andi walks back into the heart of darkness, resigned yet confident in his world.
