Sometimes a classroom needs more than a regular substitute sometimes you need a soldier.
Shale's Mercenary team is retired after a (not so) covert mission in Cuba. He becomes a substitute teacher at his teacher fiancee's Miami high school to get those behind kneecapping her. His team helps him.
Randall Thomasson is gunned down while attempting to talk his way out of a carjacking. His brother, Karl, attends his funeral and attempts to make amends with his niece, who is angry that Karl never contacted her or her father.
Students at a local college have become unusually antagonistic, and when a teacher is attacked by a gang of steroid-pumped students, Karl Thomasson—having earned a teacher's degree to facilitate his actions in the previous film—returns to the classroom to uncover the truth.
Karl Thomasson, an ex-Special Forces soldier and retired mercenary, is approached by his old army buddy Teague who gives him a mission: working undercover at a military school where Ted, Teague's nephew, is one of the cadets. Teague believes that the cadets and the student faculty are part of a white supremacist cult being run at the school. Karl accepts the mission and begins working as a history teacher at the school, seeking to expose and eradicate the cult.