In the first episode Serena comes back to New York. She sees again her "best friend" Blair, but what Blair doesn't know is that Serena and Nate (Blair's boyfriend) had sex. Chuck, who is a rich guy and also Nate's, Serena's and Blair's friend, saw Nate and Serena.
In the school Blair is giving invitations to her party. Jenny, who wants to be popular, made the invitations for Blair and as a gift, Blair gives one invitation to Jenny. Serena was not invited.
Dan meets Serena by helping her to get rid of her mum saying that they had a date.
That's virtually the part of the episode we've seen.
