In "After Twenty Years," what does "Silky" Bob's long explanation of the reason he is waiting in the doorway most clearly reveal?
The fact that Silky Bob finds it necessary to explain to the policeman walking the beat why he is waiting in the doorway shows that Bob is nervous around policemen—and as we find out later, with good reason. He is a wanted man, so just seeing a policeman is likely to cause him some anxiety. Bob is leaning in the doorway of a store, in the shadows, with no light falling on him. No doubt he has specifically chosen such an inconspicuous place to stand just so that he can avoid contact with anyone who might recognize his description from the "wanted" bulletins. When the policeman slows and then walks up to him, he immediately speaks first, "reassuringly."
This brings to mind the Shakespearean adage, "The Lady doth protest too much, methinks." By affirming something too forcefully, one mars his credibility. Let's say that Bob was not a wanted man and was not nervous around policemen. He would have probably simply nodded at the policeman and would have been surprised if the patrolman had questioned his right to be there when he was only intending to meet a friend. Instead, Bob assumes the patrolman will doubt his story, so he says, "Sounds a little funny to you, doesn't it? Well, I'll explain if you'd like to make certain it's all right." A person who was not involved in lawless activities would feel no compunction to justify his presence on the street by explaining the details of his personal situation. Ironically, by going into a long explanation of why he is there, Bob betrays his nervousness, which suggests that he is a suspicious character that the police should take an interest in.