The movie starts with the main character, Damian, getting caught in his undercover mission and fighting back against the gang to save his life. Even though Damian survived the fight, the leader of the gang has already murdered his wife.

After the scene with his wife, the film fast forwards to one year later, where Szymon Makoweicki, a history teacher at a high school, is concerned about his students as there has been an increase in drug addiction in the area.

Szymon receives a call notifying him that one of his students has passed away due to an overdose. Knowing that he cannot solve the problem on his own, he contacts his long-time friend Damian Nowicki.

Nowicki had left the police force after the tragic incident with his wife. When Szymon approached Damian with the idea of finding the culprits who are selling drugs to the school kids, he refused to help, saying that he wouldn't be of any help regarding the matter.

A few days later, Damian receives a call telling him that his friend Szymon has passed away. Szymon's body was discovered in a warehouse, and the scene has been set in such a way that it suggests he has been the leader of the gang selling drugs to the students, and for some reason, he committed suicide.

Damian decides to find the real culprit and clear his friend's name, so he takes the job as a history teacher at the same school that is at the center of the drug ring. During his first day as a teacher, he makes acquaintances with the chemistry teacher Stefan, the Polish language teacher Agata, and his other colleagues.

He is also introduced to Chmielski, the leader of the private security company, as he is hired to keep things under control on the school's premises. Later, he meets Jaisek, a student who has been supplying drugs inside the school.

On the same day, Agata gets attacked by a student who goes by the name Frog Face during some discussion in the classroom, but Damian intervenes and saves Agata. The news about the new history teacher's fighting skills spread in the school, and the students became curious to know more about the new teacher.

Damian realizes that it would be a good idea to teach his students self-defense. Together with some students, he begins his training session, but after the students leave, a group of masked men appears in the training area.

He fights back single-handedly, and he also gets injured during the fight. The next day, he sees the private security personnel with beating marks on their faces, and he realizes that the security head is the leader of the gang.

To keep Damian quiet, Chmielski creates a plan with Jaisek; later, they approach Emilia to cooperate with their plan as they threaten her to harm her father. The next day, Damian is suspended for molesting Emilia during their self-defense session.

Damian tries to tell Agata that he is being framed, but she ignores him before leaving her house. Damian grabs the school keys and sees drugs being taken away from the school, and he notices chemistry teacher Stefan making drugs.

Later, he notifies the principal about the situation in the school, and Stefan is also called, but he denies the allegations. Damian then checks the security camera for proof, but he finds that it has been tampered with.

Emilia reveals the truth to Agata, and after realizing that Damian is innocent, she makes amends with him and helps him find the culprit. They get hold of a note that Szymon left behind in his locker, which has the exact location of drugs inside the warehouse.

They visit Stefan to find the real gang leader, but before Stefan could say anything, he gets shot in the head by Chmielski, which confirms that he is one of the main members of the gang.

When they go to the warehouse, they discover that the real gang leader is principal Zamoyski. The fight breaks out in the warehouse, and Damian's students come to help him, and they manage to bring the drug ring down, and all the gang members are arrested.