it was unbelievably erotic , standing in strappy high-heels while his fingers circled her fine-boned ankles , then drifted upwards , caressing her calves , gently rubbing the hollow behind her knees , stroking her thighs , hands cupping and gently squeezing the soft roundness of her buttocks , then gliding around the curve of her hips to spread across her stomach , fingers fanning back and forth over the sensitive area beneath her hip-bones .