Lace didn't hesitate but followed Sonya's prompting.  Her tongue trailed down Billy's lower vein to his fleshy purse.  She licked at it, suckling softly at first one testicle, then the other.  She was gentle, ministering.  The way she'd been brought to the edge and left there built up tender feelings for Billy, submissive towards Sonya, but most of all excitement for what would happen next.