All in all, I was not happy with this season.
I love the acting, but that is no surprise; with Patinkin and Lewis you can't go wrong, and Clare Danes is also very good. Everyone else is rather pale, but that's no biggie.
But the gaps in the story are just too big. A lot of the things that Carrie did didn't make all that much sense, but her erratic personality made those actions not implausible.
Carrie's assumption that Brody was turned is perfectly logical. Everyone knows for a fact that Walker was turned; Brody was in the exact same situation, so people should at least be suspicious.
But no one is, for very convenient reasons:
Estes does not want to dig too deep because he is dirty; Saul does not believe Carrie because he has actually seen her in her neurotic stages; and Carrie does not believe in herself anymore for the same reason.
And since the whole CIA obviously consists of only these three people, the logical thing to put Brody under constant observation does not happen, and Carrie's assumption is just ignored.
It is normal that the good guys can't put the pieces together until the eleventh hour, so we can have an awesome showdown; but the way they did it here is just lazy writing.