My thoughts to what's going to happen this season:
Spoiler: showDr. Evelyn Vogel worked with Dexter when he was a kid (which is how she got the drawings). Due to the fact that she worked with Matthews so long ago, it would show that Dexter was just a kid. Maybe he seen a psychiatrist, or was studied by her independently by her. Now that she zeroed in on him, and has put everything together, she asked Matthews to be involved with the case that would pertain to her, specifically to 'work' with Dexter.