The entire narrative structure of "American History X" builds toward a devastating final act that re-contextualizes Derek's journey. The non-linear storytelling, alternating between the black-and-white past and the color present, juxtaposes the man Derek was with the man he is trying to become. The major twist in his backstory is the reason for his change in prison. He wasn't swayed by moral arguments alone; he was betrayed by his own neo-Nazi brethren. He discovered the Aryan Brotherhood was a hypocritical criminal enterprise involved in drug trade with non-white gangs. This disillusionment, combined with the brutal sexual assault he suffers at their hands and the unexpected kindness from his Black laundry co-worker, Lamont, shatters his worldview completely.
The ultimate plot turn is the film's tragic ending. After Derek has successfully convinced Danny to leave the white supremacist movement, and Danny has submitted his cathartic paper to Dr. Sweeney, the audience is led to believe that the crisis has been averted. However, Danny is ambushed and shot to death in the school bathroom by the same Black student he had a minor confrontation with earlier in the day. This ending is cruelly ironic. Derek's redemption does not grant him or his family immunity from the violence that permeates their world. The hidden meaning is that hatred, once unleashed, has a life of its own. Danny's murder is not an act of neo-Nazi retribution but a seemingly unrelated act of school violence, yet it is born from the same undercurrents of anger and conflict that Derek's movement amplified. The final quote from Abraham Lincoln about the "better angels of our nature" becomes a gut-wrenching lament for a peace that could not be achieved. Derek is left alive, but forced to carry the ultimate baggage: the knowledge that his past actions indirectly led to the death of the brother he was trying to save.