Mr. White refuses to help his wife open the front door because he is?
In Part Three of the short story, Mrs. White remembers that her husband made a wish for two hundred pounds using the magic monkey's paw that came true and demands that he make a second wish for their son to return from the dead. Mr. White ends up making a wish for Herbert to return from the dead, and the couple goes upstairs to bed. Later that night, Mr. and Mrs. White hear a knock at their door and realize that their son has come back from the dead. Mr. White panics and fears that his wife will open the door to witness her son's decaying, zombie-like corpse standing on their front porch, which will surely traumatize both of them. As his wife desperately attempts to unlock the bolted door, Mr. White struggles to find the monkey's paw and is able to make his final wish for Herbert to return to the grave before she opens the door. Overall, Mr. White refuses to help his wife open the front door because he does not want her to witness their son's decrepit, zombie-like corpse and desperately needs to find the monkey's paw in order to make his third wish.
He is afraid of his own son. He saw the mangled remains of his dead son and knows that he can only be a horrible monster if brought back to life. The reader can only imagine what the son looks like--if that is the son knocking at the door!! And who else would it be? Who else would be knocking at the door in the middle of the night after Mr. White, at his wife's insistence, had wished for Herbert to be alive again? What the reader is imagining is not only a Herbert who is mangled and shredded, but a Herbert who is not really "alive" but a sort of zombie who will never possess the same bouyant personality after suffering incredible pain and actually being dead. The reader imagines Herbert's appearance and demeanour through the mind of his father and can understand why Mr. White countermands his second wish as he hears his wife drawing the creaking bolt slowly back.