When the narrator shines the single beam of light on the old man's eye, that left a picture of the situation for me.
Another is when the narrator is hearing the heartbeat from under his floorboards and pacing around the room, growing more and more agitated until he finally confesses to the murder.
The quote means that Atticus is a great man who stands behind what he says and does, behaving the same in public as he does in his home. Unlike him, the others are two-faced, for example, publicly attacking Tom Robinson, while believing in the comfort of their homes that he might be innocent.
The answer to what exactly
