After witnessing a backstage murder, a punk band is forced into a back room by malicious skinheads, and must fight their way out to survive. GREEN ROOM 
Thanks. I was thinking about mentioning the MC, but it really dopes feel like one group up against the other in the film.
It is actually a little more than being stuck in a room. At first they’re forced in, but then they use the green room (and it’s locked door) to their own benefit once they learn their lives are at stake if they open it. However there is only one way in, and one way out. They have to get out, and kill.