Dexter: Original Sin will reveal details about Dexter Morgan's early life that fans never knew about. However, it's not just Dexter's life that will be explored in the prequel series, with a slew of original characters set to return. Harry Morgan is an original character that not much is actually known about, as he was already dead during the events of Dexter. Christian Slater's version of Harry could reveal a much darker side to his character.