Step 1: Understanding the Question
The question asks to identify the character who had an appointment or came to visit the secret agent Ausable in the story "The Midnight Visitor".
Step 2: Recalling the Story Details
The story begins with a young, romantic writer named Fowler meeting Ausable. Fowler is disappointed with Ausable's appearance, as he doesn't fit the stereotype of a secret agent. Fowler has come to spend the evening with Ausable to get inspiration for his writing.
Step 3: Detailed Explanation
(A) Fowler is the writer who came to meet Ausable.
(B) A policeman (or rather, a waiter pretending to be one as arranged by Ausable) is part of Ausable's clever plan but not the initial visitor.
(C) Ausable's father is not a character in the story.
(D) Max is the rival secret agent who had already entered Ausable's room with a pistol to intercept a report. He did not 'come to meet' Ausable in a conventional sense; he was an intruder.
Step 4: Final Answer
Fowler was the visitor who came to meet Ausable.