In the story "The Treasure of Lemon Brown," how does knowing Greg's thoughts and actions affect the reader's impression of Lemon Brown?

In the story, Greg's thoughts and actions greatly influence how we perceive Lemon Brown. Through Greg's perspective, we get the idea that Lemon Brown is a harmless, old man with an interesting past. 
When Greg initially meets Lemon Brown, he is wary and a little afraid. As Brown shuffles into the light, Greg takes a step back. It is only after Greg sees that Brown is an old man with a "smallish frame" that he begins to relax. Brown is also dressed in rags and "cracked, dirty shoes." Through Greg's initial perspective, we are led to conclude that Greg is a frail figure, incapable of perpetrating violence on another human being.
Later, when thugs enter the abandoned building to confront Lemon Brown, Greg begins to panic. He thinks about the pipe one of the thugs is holding, and he becomes visibly frightened. Greg thinks that Lemon Brown presents an "eerie sight," standing at the top of the stairs in his "bundle of rags." Through Greg's thoughts, we see Brown as a mysterious figure, despite his apparent fragility.
The old man surprises us, however, when he hurls himself off the stairs to tackle the thugs. We are as surprised as Greg is by Lemon Brown's action. This is because Greg has only ever seen Lemon Brown as a defenseless, fragile figure. Accordingly, Greg's perspective deeply influences how we perceive Lemon Brown.