While Harrison still spent most of New Blood knowing that Dexter had a flawed persona and past after he faked his death, changed his name, and abandoned Harrison, one flashback scene from Dexter: New Blood ’s finale episode suggests that Harrison also secretly knew that he killed Matt Caldwell the entire time.
While it appeared that Harrison didn’t know Dexter was a killer until later in the show, a flashback from New Blood’s finale hints he knew all along. Warning: SPOILERS ahead for Dexter: New Blood’s finale.
Angela reveals that Batista is on his way, and Dexter will be charged for Matt’s murder in New York and then extradited to Florida so he can go on trial for the Bay Harbor Butcher. Dexter sees the walls closing in.
Dexter and Harrison are still at odds about the boy’s new part-time job. Deb suggests Dex kill Kurt, but Dexter wants to let Angela work the case. That way Harrison will see Kurt for who he really is without putting any more distance between them.