D'Artagnan had more than once related to his friends his adventure with the stranger, as well as the apparition of the beautiful foreigner, to whom this man had confided some important missive.
The opinion of Athos was that d'Artagnan had lost his letter in the skirmish. A gentleman, in his opinion— and according to d'Artagnan's portrait of him, the stranger must be a gentleman—would be incapable of the baseness of stealing a letter.
Porthos saw nothing in all this but a love meeting, given by a lady to a cavalier, or by a cavalier to a lady, which had been disturbed by the presence of d'Artagnan and his yellow horse.