The peddler has been doing some detective work and, having discovered that Fanny was bought by Sir Thomas Booby when she was three or four years old, he is now able to reveal Fanny's family name. In his days as a drummer, the peddler had kept a mistress, who confessed on her deathbed of an incident that happened long ago while she was traveling with some gypsies. Apparently she stole a child and then sold it to Sir Thomas. The true parents of this child, the peddler says, were none other than Mr. and Mrs. Andrews — Joseph's parents! The consternation is enormous: Joseph is in love with his sister!
Meanwhile, in the privacy of Lady Booby's chamber, Slip-slop arrives with the news that Joseph and Fanny are now thought to be brother and sister. Everyone assembles at Booby-Hall, where the peddler repeats his tale; the doubts, we learn, will be resolved next day by the Andrewses themselves when they come to collect Pamela and Mr. Booby.
At dinner, Adams is in excellent form and provides some highlights later as well. Beau Didapper, amorously on the prowl for Fanny, jumps by mistake into the bed of Slipslop, who decides to bolster her sagging reputation by screaming out that she is being raped. Adams races instantly and nakedly to the rescue, but lands his blows on the bearded chin of Slipslop while the smooth-skinned Didapper darts away. Lady Booby arrives on the scene to find Slipslop held fast by her breasts, and she immediately assumes that the naked Adams has been occupied in obliging her. The embarrassed Adams whips under the sheets, and the confusion begins to clear when Lady Booby finds the remains of Beau Didapper's shirt and diamond cuff links on the floor. Lady Booby leaves, and Adams follows. But Adams is so tired and confused that he enters the wrong room and curls up in Fanny's bed, where Joseph is somewhat surprised to find him when he enters in the morning. Poor Fanny is chagrined, and Adams thinks that witches are working on him, but soon all is resolved, and Joseph guides the erring Adams back to his own room.
The initial discovery that Fanny appears to be his sister is of course confusing to Joseph, but it is only one pull of the string from an author who has constantly been in complete control. Joseph's control is also growing; he steers the erring Adams back to his own bedroom, and while Adams rejoices that incest between Joseph and Fanny has been avoided and mutters about witchcraft, we feel that the resolution engineered by Fielding's reason and clear-sightedness is just around the corner.