A bishop, knowing that King Louis XIV of France has a twin brother who has been imprisoned in the Bastille for eight years, schemes to place the twin on the throne. An abridged, cartoon version.
In their final adventure, the four Musketeers plot to replace King Louis XIV of France with the mysterious, masked prisoner in the Bastille believed to be Louis' falsely imprisoned twin brother and the true king.
The rightful heir to the throne is spirited away at birth and his twin becomes the king. When he is later recognized, the king has him locked into an iron mask, never to be seen again.