Act 4 takes place inside the Hardcastle manor. Hastings and Constance enter. Hastings informs Constance that Sir Charles Marlow, Marlow’s father, will arrive at the estate soon and that they must leave before he does, so they are not found out. Constance asks about the jewels, and Hastings assures her that he has given the jewels to Marlow for safekeeping. Hastings then announces that he will ready the horses and send a letter when it is time to leave. The two exit.

Marlow enters, followed by a servant. Through their conversation, it is revealed that Marlow has entrusted the casket of jewels to the servant, intending them to be placed in the temporary care of the “landlady,” Mrs. Hardcastle. The servant exits. Hastings enters.

Hastings discovers that Marlow has unwittingly returned Constance’s jewels to Mrs. Hardcastle. He is dismayed but does not let Marlow see it. He exits. Mr. Hardcastle enters.

Mr. Hardcastle, trying to temper his anger, informs Marlow that the servants he came with are acting irresponsibly and are currently inebriated. Marlow, failing to see the problem, dismisses Mr. Hardcastle’s concern. Losing his temper, Mr. Hardcastle demands that Marlow and his entourage leave the premises immediately. Marlow, insulted, asks that Mr. Hardcastle bring him his bill. Mr. Hardcastle ignores this and goes on to say that the letter he received from Sir Charles Marlow made no mention of Marlow’s impudence. Mr. Hardcastle then exits, leaving Marlow confused at his comment.

Kate enters, still dressed like a maid. Marlow asks her what her exact position is at the inn, and Kate corrects him, saying that he is at the Hardcastle manor, not a country inn. Having discovered the truth, Marlow is immediately mortified at how he had been treating Mr. Hardcastle. He also apologizes to Kate, whom he still believes to be a maid, for his foolishness and prepares to leave. Kate, pretending to cry, asks what it is she may have done to make him want to leave. Marlow, touched by Kate’s reaction, reveals that he has fallen for her, but he says that their difference in station prevents him from legitimizing their connection. He tells her that he must appease his father but that if it were solely up to him, they would be together. Pained, he then exits. Kate exits as well.

Tony and Constance enter and talk about how Mrs. Hardcastle is in possession of the jewels once more. Mrs. Hardcastle then enters, and the two immediately start feigning affection for each other. After a short while, a servant hands Tony a sealed letter, which turns out to be from Hastings. Despite strong hints from Constance, Tony does not realize who the sender is and hands over the letter to Mrs. Hardcastle, because he cannot make out the penmanship. Upon reading the letter, Mrs. Hardcastle learns of Hastings and Constance’s plans to elope and vows to thwart them. She exits.

Constance berates Tony for his blunder. Hasting then enters and accuses Tony of betrayal. Tony, however, insists that it is Hastings and Constance’s scrupulous planning that has undone them. Marlow then enters, accusing them all of making a fool out of him by tricking him into thinking that the Hardcastle manor was an inn. It is then revealed to Marlow that Tony is responsible for the whole deception, and the three take turns insulting Tony. Finally, Constance is called on by Mrs. Hardcastle, and she exits in distress. In an aside, Tony promises to help Hastings and Constance once more.