There are a couple of problems with the trajectory of this story, but I will not be covering that because it would ruin the story. All I will say is there is a central plot point, which is highly unlikely once you get the full picture of the story. Does this make the film less enjoyable? I don't think so. The story is engaging because of the characters, and thankfully there is little painful over explanation by the characters to tell the backstory necessary for this kind of story, in fact there are some well-done expository moments in here that break up the monotony of the single setting.
Keep in mind, this isn't a fast paced film and the tension while there, is not as high as some might like, so avoid if you don't like slow-paced films, but the acting is actually quite good here, and the characters, even though they are not extremely fleshed out, partially due to the nature of the story, are interesting. I would call this a largely character-based narrative. I also think especially with recent events the appeal of a story where people chose to be quarantined for an undefined amount of time due to a plague that has wiped out the worlds population, might have a little more appeal than it would have last year.
I have watched many of these "single room" science fictions stories, be it "Cube", "Coherence", "Infinity Room", "Fermat's Room", "White Room", "The Exam", "Circle", and every single of those is a low-budget character-based dialogue driven film, except the awful White Room, The acting is better in "Domain" than each of the other afformentioned films(Coherence is the next best acting wise). In fact, I have seen Ryan Merriaman in several TV shows and films, and was quite surprised at the nuance and the way he handled his character, who he could have easily over-acted, but he kept it quite subdued, in the best way possible, to say more would ruin it. I actually really appreciate him as an actor now and believe he deserves much larger roles.
Again, if you like science fiction, particularly of the low-budget variety, there is much to like here. It isn't gonna blow your mind, but it is a solid story with some interesting ideas, and some of the best acting I have ever seen in a low budget film, it was refreshing to see for someone who watches a lot of low budget films.
Note, this movie is not for children, it has foul language, a good deal of violence, and there is some minor sexual content, if that bugs you, though you can skip ahead a minute or 2.
Review by lyrafowlpotter from the Internet Movie Database.