the white house
Explanation:
The question above is related to the story about "Sancho and Bolsa."
William is the nephew of Mrs. Morningstar. Sancho and Bolsa are detectives and they started asking Mrs. Morningstar about William, since he was missing. Along the conversation, Sancho asked Mrs. Morningstar where William works. She responded by saying "Yes, the white house!"
So, this explains the answer.