This perhaps the most succinct telling of why this season has been garbage
In order to pull off the twist, it wasn’t possible to have Dexter doggedly pursuing the Doomsday Duo. He had to have his hands full with other things—The Tooth Fairy, Harrison’s illness, Brother Sam’s murder, Brian’s brief return—because it would strain credulity that Dexter could have meticulously observed Travis as he normally does his prospective victims, and not figure out that Gellar wasn’t real. The Ghost Gellar twist was awful to its core, a poorly executed take on a shopworn idea.
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"Occulams razor says you are scum" - masterplum