Gossip Girl (2007): Season 4, Episode 7

4 - 7: War at the Roses

Blair is caught off guard at her 20th birthday party. Worried that Chuck and Blair might return to their vindictive games, Serena and Nate make the warring exes sign a peace treaty. Dan comes up with a scheme that will allow Jenny to return to the Upper East Side to celebrate Rufus and Lily's anniversary celebration, but his plan ultimately backfires. Serena and Colin try to resist their desires for each other. Singer Robyn has a cameo at Blair's birthday party celebration.