Well my theory is that the Henry (Undying) killer is Pluto, here is why, Henry tried to scape but he couldn't, because Pluto kill him, you might say "Why Pluto and why you are to sure about that?" well, the dogs usually when they humans throw a ball or a stick and the want that they bring them back, the dogs that are good trained they usually obey, and Pluto is not the exception, he achieves "killing" Henry, he hide Henry's boddy in a Mickey suit, then Pluto gives to the Mother some of Henry parts, his eyes, his teeth, his vocal chords and skin, the mother doesn't use the skin, but the other parts are used to The face, Disembodied and Impurity, then Henry is alive in the Mickey suit Pluto go to the Pirate Caverns, Henry take revenge on Pluto before being another person, he punch pluto and this one ends more broken than before, Pluto now is kind, he doesn't attack you in the nights because he have the fear of being more damaged by a victim, the Henry story is the same in the original FNATI, thats why he tell to Pluto to shut up and pluto obey because he know how is Henry, well thats everything thx for your atention.