(The first of two companion Three Musketeers movies produced by Alexander Salkind. The movies were going to be one longer epic, but to make more money, the producers split them into two movies without telling the cast. A lawsuit ensued and now the "Salkind clause" exists so that a cast must be informed how many movies they are expected to be a part of.)
D'Artagnan (Michael York) leaves home to become a Musketeer and encounters the three Musketeers, Athos (Oliver Reed), Porthos (Frank Finlay) and Aramis (Richard Chamberlain) whom he each insults. When the three Musketeers arrive to watch Athos duel d'Artagnan, Cardinal Richiieu's (Charlton Heston) guards led by Rochefort (Christopher Lee) attack and d'Artagnan helps the Musketeers defeat them.
Adventures ensue when Queen Anna (Geraldine Chaplin) gives her prize jewels to her lover, the Duke of Buckingham (Simon Ward). When her foppish husband, King Louis XIII (John-Pierre Cassel), demands she wear the jewels to his birthday celebration, the Musketeers must journey from France to England to recover the diamonds.
The villainous Milady de Winter (Faye Dunaway) is sent to seduce the Duke of Buckingham and steal two of the diamonds. D'Artagnan arrives to pick up the necklace and when they discover that two diamonds are missing, the Duke frantically has two more jewels created so d'Artagnan can return to France with a full set.
At the ball, King Louis confronts Queen Anna about the missing necklace. The Musketeers defeat the Cardinal's guards and d'Artagnan's lover Constance (Raquel Welch) overcomes Milady de Winter so that the two replacement diamonds can be set in the necklace. When Cardinal Richelieu produces two of the missing diamonds, Queen Anna thanks him for the gift, since she is wearing a full set of diamonds.
For his heroism, d'Artagnan is promoted to a Musketeer while Milady de Winter and the Cardinal plot their revenge.
Thanks Evil Ed!