All parties show up at the designated meeting place: a little spot behind the Luxembourg. (Usually this is where the goats are fed, but Athos throws the goat-keeper some money and the lackeys are stationed as lookouts.)
The Englishmen tell the Frenchmen their names and rank.
D’Artagnan, Athos, Porthos, and Aramis give their (fake) names, much to the annoyance of the Englishmen, who think those names belong to shepherds and not to gentlemen.
(Historical Context: It was very important that you fight with people you considered worth your time. If a peasant insulted a duke, for example, they wouldn’t have a duel. The Duke would just order the peasant hanged. Duels were for noblemen, and noblemen at this time just didn’t go by "Porthos.")
The Englishmen point out that they’re not going to risk their blood by fighting a bunch of unknowns.
Athos, Porthos, and Aramis take their adversaries aside and whisper their true names and ranks.
Athos tells his opponent that now he has to die.
Finally, the duel starts: Athos kills his opponent; Porthos wounds his in the thigh; Aramis’s opponent turns and runs away.
D’Artagnan fights defensively and disarms his opponent. He puts his sword point at the man’s throat and tells him that he spares the man’s life only because of the man’s sister.
The Englishman is impressed with all of them.
Porthos and Aramis turn their attention to the dead man, whom they undress in order to ascertain the extent of the wound.
As they do so, a giant bag of money falls out. D’Artagnan gives it to the Lord de Winter (his opponent) so that he may give it to the dead man’s family.
Lord de Winter tells him not to be ridiculous and suggests they give the purse to the Frenchmen’s lackeys. He offers to introduce D’Artagnan to his sister that very evening.
Athos asks D’Artagnan what he plans to do with the money.
D’Artagnan replies that he was going to give it to Athos, who rightfully owns it since he killed the previous owner.
Athos says they should give it to the lackeys—the Englishmen’s lackeys. Athos executes his own opinion, much to Porthos’s sadness.
Lord de Winter gives his sister’s address to D’Artagnan and tells him to show up at eight that evening.
D’Artagnan feels inexplicably drawn to Milady, even though he knows she’s an agent of the Cardinal.
He gets ready for his big night at Athos’s place, who continues to warn him against this woman.
Lord de Winter picks up D’Artagnan, and the two head over to Milady’s place.
Milady has a beautiful new home, proving her lack of concern over the war between England and France. (Remember, she’s an Englishwoman.)
Milady appears to be upset when she learns that Lord de Winter owes his life to D’Artagnan, but she hides it well and her brother fails to notice.
The maid comes in with a message for Lord de Winter that obliges him to leave.
D’Artagnan and Milady continue to hang out. He learns that she is technically Lord de Winter’s sister-in-law; she had married his younger brother and bore a child. (He is also convinced that she’s really a Frenchwoman, because her French is really impeccable.)
D’Artagnan flirts incessantly with her.
On his way out, he brushes past the maid, who gives him come-hither glances.
D’Artagnan continues to visit Milady every night, and every night the maid finds an excuse to brush past him on his way out and give him come-hither glances. D’Artagnan is falling so much in love with Milady that he does not notice her maid falling in love with him.