In "The Monkey's Paw," what was the White family's last wish?

Actually, the last wish was only Mr. White's. Both husband and wife believed their son Herbert had come back from the dead as a result of their second wish. Mr. White was horrified at the prospect of seeing Herbert as he must look after being mangled in the machinery at work and then being dead and buried for ten days. Mrs. White, on the other hand, was anxious to open the door and hug her son. Unlike her husband, she had never seen his body and had no idea how horrible he must look. The tiny woman was having a hard time opening the door because one of the bolts was too high for her to reach.

"For God's sake don't let it in," cried the old man, trembling.

"You're afraid of your own son," she cried struggling. "Let me go. I'm coming, Herbert; I'm coming."

The reader has been made to believe that it must be Herbert doing all that knocking and dreads seeing the living-dead monster if Mrs. White gets the door open. Herbert was introduced as a good-natured, funny young man full of high spirits. But if he came back to live with his parents after being dead and buried, he would not be the same Herbert. The feeling produced here is uncanny. Imagine having to live with such a creature!

So Mr. White finally makes a decision of his own. The first wish was suggested by Herbert, and his father wished for two hundred pounds. The second wish was forced on White by his wife, who insisted that he wish for Herbert to come back to them. The third and final wish was White's alone. We do not know the exact words he said, but he obviously wished that the knocking would cease and the person knocking would go away forever.

"The bolt," she cried loudly. "Come down. I can't reach it."

But her husband was on his hands and knees groping wildly on the floor in search of the paw....He heard the creaking of the bolt as it came slowly back, and at the same moment he found the monkey's paw, and frantically breathed his third and last wish.

The knocking ceases as soon as he makes the wish. When his wife opens the door there is no one there. Mr. White follows her outside and then runs down to the gate.

The street lamp flickering opposite shone on a quiet and deserted road. 

Was it really Herbert out there, or some lost traveler seeking directions? If it was a real human being knocking, where did he disappear to?