Just caught the episode. I guessed early on that they were setting up false suspense over the kill room. Of course, my roommate had to chime in and remind me that, back in season one, Dexter did his killing in remote places, if possible. That in mind, I see no reason why they didn't just take Alex whats-his-name far away from there, just to be safe (the answer is, of course, that the writers wanted to set up some false suspense).
I'm not sure how I feel about turning Dexter/Lumen into a romantic entanglement. The writers will have to do more work to differentiate it from Dexter/Lila if they want to do something with it. Lumen is more stable, at least, but I keep getting the impression that the writers are waiting for another shoe to drop when it comes to her character. After seven or eight episodes, we still don't know a whole lot about her.
And, it certainly looks like Manny Coto has something about abusing Peter Weller on his shows. His character is definitely toast by the end of the season.