Let's start at the beginning: two strangers--both of them men--meet in a field at night for, what appears to be, anonymous and consensual sex. For one of them, it's the first time, and he's extremely nervous. After some reaffirmation that everything will be okay from the other man (Jimmy), the newbie begins to get undressed. At this time, four skinheads appear out of nowhere and attack the vulnerable--and more than likely closeted--"faggot". The non-fatal coup de grâce comes in the form of a running kick to the poor kid's face. Everyone rejoice in celebration of the savage brutality against all things that go against nature!
Moving on: we meet a disgraced serviceman, Lars, who, rather than being promoted, is dismissed due to rumors that he made a pass at a fellow serviceman. Feeling lost, confused, purposeless, he moves back home and soon becomes enmeshed in the Brotherhood: a group of neo-Nazis that plan unrelenting attacks on Muslims, homosexuals, Pakistanis, anything that isn't deemed "natural" by them.
The film focuses on the friendship (relationship) that Lars and his fellow brother, Jimmy, develop over the course of molding Lars into a full, lifetime member of the Brotherhood. The filmmakers succeed in making you feel sympathy for these men despite the fact that they are filthy fucking scum and deserve a permanent place in hell (if there ever was one).
Love is love, and it knows no limitations. However, love can exist alongside hate, and that's yet another point, I feel, that the filmmakers are trying to make. Our basic human nature allows us to do both: love and hate. They loved each other, even in the face of losing everything they lived and breathed for, including their own lives.
Jimmy's brother, Patrick, discovers their romance, and is forced to choose between two loyalties: that to his brother and that to his brethren. Unfortunately, he chose the latter. Lars and Jimmy are fooled into thinking they are being treated to a surprise in relation to Lars' recent initiation into the Brotherhood, when in reality, they were being taken to a field where Jimmy would be faced with a choice: you kill Lars, or we kill you both. Luckily, but quite sadly, it ended up with Jimmy reluctantly beating Lars within an inch of his life.
They are let go and decide to finally runaway together to be happy. They go back to the house where they were staying and pack up their things; Jimmy helps Lars into the car, and closes the trunk of the car...
This is when the filmmakers really fuck with your mind.
Okay, so you've seen these two men suffer from violence and alienation, and you've empathized with them and their struggle. You've (perhaps) put it all behind you that they are neo-Nazi scum and do not deserve a single tear shed over any kind of harm--emotional, physical, or otherwise--they may endure. Well, as Jimmy is closing the trunk, a man comes up from behind him and stabs him deep in the chest. At first you think this is just a final retaliation from the Brotherhood, but no; it's someone else; it's someone who does deserve sympathy.
A few days prior to this happening, Jimmy was shopping in a hardware store, and the clerk that rang him up was none other than the gay kid from the beginning of the movie. They quietly acknowledged each other, but nothing was said beyond the standard customer service transaction: he rang up the items, Jimmy then paid and left. Presumably, he followed Jimmy home, and mustered up the courage to retaliate against his attacker.
The closing scene ends with Jimmy on life support in the hospital, with his brother, Patrick, sitting at his bedside, feeling the remorse of having put his loving brother in this position. Lars arrives and replaces Patrick at the bedside, but not before they express sorrow and thanks to each other in a wordless exchange. The end.