A young programmer whose job is to watch over the reality-warping Cube defies orders to rescue an innocent mother trapped in one of its rooms.
Cube Zero completes the trilogy of Cube movies which are based upon people waking up inside of giant multiroom cubes filled with death traps and having no knowledge of how they got there or how to get out. In this film, the viewer finally sees what goes on behind the scenes (save for a snippet at the end of Hypercube), though since this is the first film chronologically, it does not necessarily follow that this is how things worked in the other two films. However, you will finally learn a little about the likely backstory of Kazan from Cube 1.
If you are looking for a film with a feel good ending then you've chosen the wrong trilogy. The ending of this one is a mixed bag. Who the bad guys and good guys are is a matter of opinion and you may change your view from the other two films. I personally feel this film was the weakest in the trilogy since there is a lot of focus on what goes on outside the cube and less focus on character development inside the cube. It is still well worth watching. If you have not watched the other two Cube films, I do recommend watching them first and saving this one for last so the background revealed here doesn't spoil their viewing.