Inside the Larrabee house the next day, David is lying on his front because his butt hurts.
Linus comes in and tells David that Sabrina was disappointed but not angry.
Linus has also designed a plastic hammock for David with a hole in the bottom he can put his butt through.
David asks Linus to keep an eye on Sabrina. He wouldn't be so keen if he'd seen Linus kiss Sabrina.
Elizabeth shows up to take care of David. She's suspicious of what the champagne glasses were doing in his pocket.
Then she gets distracted when David falls through the hammock and bashes his butt.
Poor butt (you could go through much of the second part of the film just saying, "poor butt.").
Linus leaves to go sailing with Sabrina.
He goes into his room to change for the boating outing, opens his closet, and discovers his dad in the clothes closet smoking (Oliver thought Linus was Mrs. Larrabee, and didn't want her to see him smoking.)
Linus explains that he's going to make Sabrina fall in love with someone else—namely Linus himself.
Linus says he'd much rather be doing business deals than romancing Sabrina. So basically he's off to lie to her.