It's Serena and Dan's official Engagement Party. Lily, Eric, Rufus, Jenny have been in New Haven for a couple of days.
At Serena's house the party preparations are in their final stages and it is early afternoon. Blair has been at the house helping out for almost an hour now. Serena had tried to get Blair to tell her the reason she came to her house a few nights ago night but Blair keeps telling her it was nothing.
Chuck now arrives at the house, invited by Serena. Serena has told Chuck and Blair (separately) that she has a surprise for them.