Unknown is a mystery thriller about five guys who wake up in a warehouse without any memory, and they try to figure out who they are and what happened.
Now this movie does a good enough job of creating the suspense, the setting and the characters so that you are invested enough to be thrilled. You try to figure out who's right and who's wrong, who's good and who's bad, and stuff like that along with the characters, hooking you in the movie.
The acting was good enough to sell this premise. And just like the characters are doubting their-selves and each other, you start to do the same, which is a job well done for a movie like this.
The bulk of the movie takes place in the warehouse, but there are scenes of the law enforcement side, which aren't as interesting, and hence break the pacing a bit. Nothing too serious, but worth mentioning.
Now, unfortunately, two things in particular ruined the movie for me. First, the ending. In hopes of trying to one-up itself at every turn near the end, the movie got lost in its own twists, and instead of ending on a high note, it ended on a whimper, at least for me. Secondly, some information gets known to you a bit too early in the movie, lessening the tension in the warehouse.
This could have been a decent mystery thriller, but some poor decisions brought it down to the So-So level.