The motto of the four was "all for one, one for all." D'Artagnan had already earned the dislike of Cardinal Richelieu by his part in the fight with the cardinal's guards; it was not long before his daring gave greater cause for offence.
The king suspected his wife, Anne of Austria, of being in love with the Duke of Buckingham, and the cardinal suspected the queen of intriguing with Buckingham against France. Now, a secret interview had taken place at the palace between Buckingham and the queen, and the cardinal, who employed spies everywhere, found out this as he found out everything, and determined to destroy the queen's reputation, for there was deadly enmity between Anne of Austria and Richelieu.
Buckingham had received from the queen a set of diamond studs--a present from the king--as a keepsake; so the cardinal despatched a certain lady, a woman of rare beauty, known as "Milady," to England, to get hold of two of these studs.
Then the cardinal, by fostering the royal suspicion, persuaded the king to give a grand ball whereat the queen should wear the diamond studs. By this means Louis would be convinced of Buckingham's visit, for the set of studs would be incomplete.
The queen was in dispair. It was D'Artagnan and the three musketeers who saved her honour. D'Artagnan loved Madame Bonacieux, a confidential dressmaker of the queen's; and this woman, devoted to her royal mistress, gave D'Artagnan a secret note from the queen to Buckingham.
D'Artagnan went at once to M. de Treville, obtained leave of absence for himself and his friends, and set out for England. It was not a minute too soon, for the cardinal had already made plans to prevent any such counter-move, giving orders that no one was to sail from France without a permit.
Between Paris and Calais, Porthos, Aramis, and Athos were all left behind, wounded by Richelieu's guards, and D'Artagnan only effected a passage to Dover by fighting and nearly killing a young noble who held a permit from the cardinal to leave France.
Once in England, D'Artagnan hastened to find Buckingham. The latter discovered, to his horror, that Milady had already become possessed cunningly of two of the precious studs, and D'Artagnan had to wait while the skill of the first English jeweller made good the loss beyond detection.
He returned to Paris with the twelve studs in time for the royal ball. Milady had already given the two she had stolen to the cardinal, who had passed them on to the king.
"What does this mean, Monsieur le Cardinal?" said the king severely, when in the middle of the ball he found, to his joy, that the queen was already wearing twelve diamonds.