Man, what an incredible episode. This is what's known as a bottle episode; that is, an episode which uses as few characters and locations as possible. Usually they're done for budgetary reasons, but sometimes a more artsy show like this one will do one for effect. The intended effect in this case is claustrophobia; we're trapped in this apartment with these characters for an hour, with no commercial breaks and no scene changes to allow us a reprieve.
And yet, while the limited setting undoubtedly creates a sense of claustrophobia, it also weirdly lends a grandiosity to things. The episode feels very much like a stageplay, a feeling which is reinforced by a series of intertitles throughout the episode proclaiming the beginning of five different acts. This structure gives a strong feeling that the episode is building towards something, and it most certainly is; near the end we get one of the biggest and most devastating twists of the series.
I'd be lying if I said that I went into the episode without expectations, given the way the network has been hyping it up, but it blew me away regardless. If you haven't watched it yet, avoid the internet like a plague until you have. It's a big one.
