Restoration, Farquhar needed to please a public that was used to naughty shenanigans but was newly awakened to calls by Jeremy Collier for moral reform of the stage.
Technically, "beaux" is the plural of "beau" meaning a male admirer. The two beaux in the play are Thomas Aimwell and Francis Archer, who are both intent on marrying wealthy women to get out of financial difficulty. Because they are in such reduced circumstances, Archer agrees to pretend to be his friend's servant at a country inn. If Aimwell can't catch an heiress, then he'll pretend to be Archer's servant at the next stop.
Aimwell ends up falling for the charming Dorinda, sister to an unhappily married blockhead named Squire Sullen. (Seriously. The cast list describes him as "a country blockhead, brutal to his wife.") Dorinda is dutiful to her brother, but more sympathetic to her sister-in-law. Mrs. Sullen longs for the pleasures of London, but her husband is just interested in getting drunk on country ale. Though Farquhar depicts Mrs. Sullen as occasionally silly, he portrays the squire as completely incapable of sympathizing with her or anyone.
A group of criminals led by a highwayman appropriately named Gibbet add some interest to the play and get the plot stirring. Aimwell and Archer end up saving the Sullen household from being robbed, and their valor helps to convince Dorinda to agree to marry her suitor. The problem is that Aimwell has been lying to her, pretending to have a fortune that actually belongs to his older brother. How could Farquhar make this cad no longer a cad anymore? By having the older brother suddenly die, granting Aimwell the fortune after all. Problem solved!
Unfortunately, this did not solve the problem of the Sullens' unhappy marriage. To me, the most remarkable part of the play is when Farquhar has them agree to an amicable separation. Some important papers saved from the robbers content the squire, while Mrs. Sullen and her brother are allowed the return of her dowery. Squire Sullen even invites people to "celebrate my sister's wedding and my divorce" at the same time.
Chance magically converts Aimwell into an honest man, but perhaps Farquhar thought it was a bridge too far to ask the audience to believe in Sullen having a reformation and tending to the needs of his wife. In any case, the play's conclusion surprises, even more than 300 years after it was written.