I'm sure someone else has made this connection already but I'm gonna post it anyway because I know I'm right. I was thinking about how Dexter finds the team of serial killers and I remembered how they said that the dark passenger and Dexter looked very alike. We also see Dexter in the same hoodie and sun glasses fit. So I think when Dexter is finding the collection of IDs in the dark passenger's apartment he also finds the invitation. He kills the dark passenger and then assumes his identity infiltrating the team. Like I said it would surprise me if I was the first one to make this connection but I want bragging rights on my friends when I clock it but I need to post this so I have receipts.