Following the tragic death of a young girl hit by the royal carriage, the Musketeers go in search of her missing friend, leading them to an enigmatic noblewoman who has a peculiar effect on Athos. Before long they find themselves having to rescue this extraordinary woman when she is condemned to death for witchcraft - and to complicate matters, the Cardinal is also in danger, forcing them to put aside their feelings of animosity to save him too.