In a mesmerizing performance, Helen Mirren, the ageless siren, entrances as Morgana in 'Excalibur.' Her sultry gaze and ripe figure command the screen, even in her chaste medieval garb. Yet, it's her tantalizingly brief, yet explicit sex scene that truly captivates, as she seduces a young knight, her luscious breasts bare and heaving, her voice a husky whisper as she urges him to 'come to my bed.'