on a darkened staircase a woman on her knees performed the act for which she was being paid , the man above her holding money in his hand over her head ; a young couple , two obvious addicts in near frenzy , were pleading with a man in an expensive black leather jacket ; a small boy , smoking a marijuana cigarette , urinated against the stone wall ; a beggar without legs clattered on his wheeled board over the cobblestones chanting 'bong ngo .