After learning his long lost brother is a test subject in a government experiment, a reckless government agent teams with terrorists in a post-apocalyptic wasteland to mount a rescue.

I know you really want to say that the setting is a post-apocalyptic wasteland, but I don't think it works where you put it. To me, it reads smoother this way, "... a reckless gov agent teams with terrorists to mount a rescue."

My last comment is more aesthetic. You waited until the middle of the sentence to tell us who the sentence was about. Personally, I think it could be stronger if you started the sentence with the subject. For instance, do this, "A reckless government agent learns... and teams with terrorists..."