The Substitute

Shale, a Vietnam veteran and mercenary, completes a covert operation in Cuba that goes disastrously wrong, leaving three teammates dead. He returns to Miami haunted by the mission and its casualties. The failed operation sets him on a path toward protecting his girlfriend and confronting local gang violence.

Shale shows up unannounced at Jane Hetzko's apartment and she warmly welcomes him back. His reunion hints at a close relationship and shows his desire for stability despite his violent past. Jane is a schoolteacher at Columbus High School and is unaware of the dangers looming.

During a morning jog, Jane is attacked and suffers a broken leg, which Shale suspects is linked to the Kings of Destruction gang. The assault heightens his resolve to protect her and uncover the gang's influence. This incident becomes the inciting event that drives him to go undercover.

To keep watch on the gang's operations and protect Jane, Shale poses as an Ivy League–educated, government-affiliated substitute teacher at Columbus High. He quickly learns the school's grim conditions and the trouble its students cause. His undercover status also allows him to monitor the gang's activity from within.

On his first day, Shale struggles to control a chaotic class of under-educated students. He uses his street-smarts and military training to regain authority, eventually gaining respect through decisive self-defense when students lash out. The moment marks his transition from outsider to effective mentor.

As he earns the students' trust, Shale bonds with them over shared experiences of struggle, and he befriends fellow teacher Darrell Sherman. He also encounters Juan Lacas, a student who is secretly a gang leader. These connections deepen the web of loyalties around the school.

Suspicion grows as Shale installs surveillance cameras and uncovers that Juan is orchestrating the attack on Jane and secretly works with Principal Rolle to run a narcotics ring. The grim discovery reveals the school's hidden role in a broader crime operation. He plans actions against them.

Shale and his team raid a drug deal on the school grounds and seize the money. They present it as a donation to the school to purchase music and sports equipment, exploiting it to fuel a legitimate-seeming front. The raid exposes the pipeline and triggers a chain of revelations.

After the raid, Sherman and a female student, Lisa, witness drugs being loaded onto a school bus. Sherman initially denies the implications, but the evidence forces him to confront the corruption within the school. Their discovery ties the faculty and administration to the narcotics operation.

The day after the witness accounts, Sherman hides Lisa under a stairwell to delay pursuers, creates a diversion, and sacrifices himself to ensure the others escape. His death underscores the cost of confronting the gang inside the school. Lisa survives by escaping with Shale's help.

As Shale is away, Jerome runs the class; Lisa seeks out Shale and Jerome takes her to Jane's house, knowing Shale will return there. The plan mobilizes the characters to reunite and protect Jane from the gang's advances. It deepens the web of loyalties around Shale.

Rolle sends Juan to hunt Jane; Shale races to her apartment and crosses paths with him. In a tense confrontation, Shale kills one attacker and incapacitates another, but Juan uses Jane as a human shield. A neighbor's distraction allows Shale to break free.

Jerome, who had been tied up with Lisa, shoots Juan from behind, ending the standoff. Shale then frees Jane and realizes the gauntlet has shifted in his favor. The act marks a turning point toward reclaiming control of the situation.

With the immediate threat to Jane resolved, Shale learns that Columbus High is being used as a distribution center for cocaine. He organizes his team to retake the school grounds and prepare for a full confrontation. The revelation expands the scope of their mission beyond individual danger.

Shale and his ally Joey Six confront the remaining KOD members, Johnny Glades, and Janus’s mercenaries along with Rolle on the school grounds. They kill all the dealers and emerge as the sole survivors of the battle. As credits roll, they walk away discussing future operations as substitute teachers.