In the previous season, David Oliver is tortured in order to acknowledge that information about the whereabouts of Syd. The third season completes the series after David was able to defeat Farouq, and thus reveals the true face of the enemy at those critical moments. There is still one hope of revealing the full details of this enemy.
The Xavier stuff works like gangbusters and it's a shame that his journey into Farouk's web wasn't interspersed throughout the season like last season's lessons on insanity.