I suspect that Sarah knows exactly who was the former occupant of the coffin in the mausoleum. With massive understatement, she tells David that he "went away." Even though Sarah doesn't answer his questions and insists that the former occupant did leave the coffin, David is delighted to have yet another secret to keep.
Vicki has made the connection between David's little friend and the "girl at the top of the stairs," whom she glimpsed at Barnabas's party.
Barnabas has one of the great lines of the show in a defining moment of his relationship with Julia: You are a meddlesome and domineering woman. If the modern man is willing to tolerate your kind of woman, that's his problem, but I will have none of it.
He tells Julia he will handle Burke with finesse: "a quality that seems lacking in your world."
I love Barn's feigned innocence when he tells Vicki oh, so reluctantly that Burke is having him investigated. What should I do? he asks her with becoming diffidence. Of course Vicki instantly says she'll speak to Burke and make him stop. Then Barn has the gall to apologize for troubling her. Finesse indeed! I just hope JF enjoyed these bits as much as we do.
Julia returns to Collinwood, and she and Barn keep up their pretense of distance by addressing each other as Mr. Collins and Miss Hoffman. Barnabas listens tensely as Vicki tells Julia that David saw his friend Sarah again and that they played in a secret place. Barnabas leaves hastily.
David comes downstairs and announces that he's hungry, but Vicki says she'll have Mrs. Johnson fix him something. She refuses to let him go to the kitchen--most likely because he won't clean up after himself.
Another fabulously moment from JF: From outside the mausoleum, Barnabas hears Sarah playing her flute, but when he draws near the gate, the music stops. No, Sarah, don’t stop, he begs her. Inside, Sarah sits on her stone coffin, listening intently--and silently. His face and voice suffused with sorrow and longing, Barnabas says, It’s your brother, Barnabas. I’ve come to take you home again. But when he enters the mausoleum, it’s empty. If a vampire could shed tears, Barnabas would be near weeping. Leaning his head against the cold marble of her plaque on the wall, he pleads, Sarah, come back. Please come back. I need you, Sarah. I love you, and I need you. But the only reply is silence.
Lydia, your observation about that scene is great! Barnabas learning just how little control he has over the people in his orbit.