The final episode in the saga of The Three Musketeers finds Aramis attempting a royal coup. Philippe, the 'man in the iron mask', has been a prisoner in the Bastille for eighteen years. He is also King Louis' twin brother. Aramis attempts to install Philippe in Louis' place, in turn imprisoning the King of France. D'Artagne must defend his king, even if it means he must kill a fellow musketeer.