Milady, they learn, is going to London to make sure that the duke of Buckingham is killed; in return, the cardinal will take revenge against d'Artagnan. The musketeers immediately decide on a plan to warn d'Artagnan and Buckingham. Thus, when Milady arrives in England, she is taken prisoner by her brother-in-law, de Winter. However, she cleverly corrupts her jailer, convinces him (a religious puritan fanatic) that Buckingham deserves to be put to death, and he obeys her.
She then escapes to France, where she is determined to complete her revenge against d'Artagnan. She goes to the convent where the queen has placed Constance Bonacieux, d'Artagnan's beloved, for protection, and there Milady wins the young girl's confidence. Precisely when d'Artagnan and the musketeers arrive to rescue Constance, Milady poisons her and escapes.
D'Artagnan and the musketeers track her down, accuse her of her many crimes — and execute her. When the entire story is revealed later to the cardinal, he is horrified at the extent of Milady's evil web of death, and he is extremely impressed with d'Artagnan's laudable actions. Consequently, he writes out a commission for d'Artagnan to become a lieutenant in the King's Musketeers. After offering the commission to Athos, Porthos, and Aramis and being refused by all three, d'Artagnan accepts the prestigious commission at the early age of twenty-one.
