I think it's safe to say, heading past the halfway point of the season, that this is the weakest season yet. I don't even have to wait to see how the season will finish, it's obvious that the writing is aimless and even if the acting is somewhat solid (especially with Mos Def and Michael C. Hall, of course), it doesn't excuse the ridiculously misguided plotting.
That being said, this episode was a nice change of pace from the lame Doomsday Killer stuff. We get to see Dexter's Dark Passenger replaced with his brother Brian, who grabs a hold of his damaged psyche and makes him kill without following the code. If Harry acts as the person trying to keep Dexter on track, Brian is the one trying to make him go off the tracks. This all begins after Dexter learns that Trinity has struck again in Nebraska, this time killing his wife and daughter. Of course, Dexter knows this isn't possible since he killed Trinity two seasons ago. Which means it must've been Jonah. Dexter decides to take a five day road trip to Nebraska.
The road trip acts as a means for Dexter to let his id run loose. He hooks up with a woman on the road, steals a gun, kills a weed farmer and nearly kills Jonah. It's a tumultuous road trip, and the whole time, he has Brian right behind him, making him do these things.
This sets up some issues between Deb and Dexter. Deb needs Dexter to be there for her and help with the Doomsday Killer case. Tension between Deb and Dexter can only mean great developments in terms of the long-term story being told in the show (which means Dexter being caught). However, it doesn't help that the show focuses on pointless crap.
This includes, sadly, the stuff about Travis Marshall and Geller. When I heard Colin Hanks and Edward James Olmos were guest-starring this season, I grew excited at how the show would use them. Instead, their characters ended up doing nothing exciting and Mos Def jumped ahead as the stand-out. Right now, Marshall is hanging out with his sister while Geller (who is probably not real, yet the show insists on making us believe he is) tries to get him back to work. It'd help if we could figure out what the heck their plan is, but right now, it makes no sense.
I'll never bail from the show, but right now, it's really hard to justify this show staying on. It should've ended after five and they should've given the show a different ending so it could've gone out on a higher note.