In her next letter home, we learn why Pamela had to sign off so quickly: Mr. B was coming.
Because she writing a letter about her boss's naughty behavior, she acted pretty guilty.
Mr. B then lit into her for not welcoming him home. (With what, slippers and a sandwich?)
He's also ticked off about two other things: telling Mrs. Jervis about the harassment, and writing a letter.
Pamela tries to get out of answering his accusations, but she eventually cops to both charges.
After some arguing back and forth, Pamela succeeds in making the master ashamed of his behavior, and he storms out of the room … only to come back a few minutes later and say that if Pamela is going to smear his name, he might as well deserve it.
She tells her parents that he "offer'd to take [her] on his Knee, with some Force" (18.11).
To make matters even worse, he made fun of her concern for her own honor; in his view, she is silly to worry about it at all, since she couldn't be held responsible for an act that she has no power to resist.
He said, "Pretty Fool! . . . how will you forfeit your Innocence, if you are oblig'd to yield to a Force you cannot withstand? Be easy . . . for let the worst happen that can, you'll have the Merit, and I the Blame, and it will be a good Subject for Letters to your Father and Mother, and a Tale into the Bargain for Mrs. Jervis" (18.11).
Um, if that's what Mr. B thinks, then he's obviously never heard of victim-blaming.
After a struggle, she managed to get away from him into another room, locked the door, and promptly fainted. Of course.
Mr. B saw this through the keyhole and then summoned Mrs. Jervis to attend to her.
To explain the scene to Mrs. Jervis, the master blamed everything on Pamela's being a "fool" in response to his "kindness" (18.32). He seemed resolved to kick her out of the house, which Pamela reports would suit her just fine.
He's arranged to have Mrs. Jervis bring Pamela to him the next day and invited Mrs. Jervis to stay and hear everything that goes on between them.