At the end of the premiere, it looked like Vogel was going to cause some serious problems for Dexter, but it turns out she's actually on his side. Harry went to her when Dexter was only ten and confided his fears that Dexter was a psychopath. Vogel helped Harry focus Dexter’s urges, and she helped him come up with the code. Now she's asking for Dexter's help in return.
The Brain Surgeon, as they're calling this season’s killer, is sending the pieces of brain he scoops out of his victims to Vogel. She thinks it could be a threat from one of the other psychopaths she treated and she asks Dexter to help hunt him and kill him before he kills Vogel.
The revelation that Harry went to someone for advice with Dexter is huge for Dexter, and at first he doesn't trust Vogel. But eventually he comes around and agrees to help her. He even admits he would have liked to have known about her earlier so he could have talked to someone after Harry’s death.
Vogel is the first real mother figure we've seen for Dexter. Doris (his adoptive mother) died when he was 16, and she's hardly present in the series. Not only that, but she never knew about Dexter's psychopathic tendencies. Vogel, on the other hand, knows everything there is to know about Dexter and she doesn't judge him or push him away. In fact, she feels proud of him, and tells him he is a gift to the world. At the end of the episode, when Vogel hugs him, Dexter looks as if he's going to cry. Harry was never proud of Dexter, not really. Having someone who believes in him could bring out a side of Dexter we've never seen before. His relationship with Vogel should prove to be a very interesting aspect of this season.
But while Dexter might be changing for the better, Deb continues to spiral more out of control. She checks out Briggs' apartment to see if she can get a lead on the storage key she found on his body. When she finds an address for the storage facility she heads over there alone. She finds the jewels, but El Sapo shows up and takes her gun and the jewels. Rather than let him go, however, Deb attacks him and tries to get the jewels back. After a pretty intense fight between the two of them, El Sapo leaves with the jewels. But we soon find out that someone murdered El Sapo, and that someone was Deb.
It's clear at this point that Deb doesn't care what happens to her. She recklessly fought an armed man when she had no real way to defend herself, and then she took it a step further and killed him. When Dexter confronts her about it, she can't even remember how it happened. Dexter finally admits that the woman Deb used to be died when LaGuerta did, and he doesn't know how to handle the woman she's become.
While the Brain Surgeon will obviously play a large role as this season's main villain, the real story is going to be Dexter's new relationship with Vogel and his changing relationship with Deb. And let's not forget that we haven't seen the last of Hannah.