Even without much of a story to speak of, "Sister" is still a harrowing tale of survival on the edge. As such, sometimes it is a little hard to watch but in the end is quite worthwhile. That is set around a classic separation of the classes who only rarely meet on personal terms. But in this fictional world, things are rather topsy turvy, encapsulated in the enigmatic final shot and symbolized by a huge plot twist 2/3 of the way through that while maybe a shock is actually not all that surprising.
Very subtle film that does challenge you a little.
Gillian Anderson is barely in it. Not sure why she has top billing. Her character is really nothing here and could easily have been omitted.