Periodically, his free hand floated up and his thick fingers batted at something in the air. They made slow stroking motions, up and down, side to side, as if he were caressing an invisible pet. One of his sleeves retracted, and I saw marks on his forearm - I’d seen those same tracks on homeless people living in grimy alleys in San Francisco.
Amir makes this observation about the Talib in Chapter 22.
What does it imply?