Thanksgiving in the Waldorf household finds Blair upset that her mom's new boyfriend, Cyrus, has decided to ruin all her favorite traditions, but that's nothing compared to what's coming next. Lily finds herself trying to broker a peace treaty between Rufus and Jenny who is prepared to cut off all communication with her father if she doesn't get her way. Serena isn't quite ready to come clean with Aaron about her complicated past, but Dan ends up accidentally revealing a few tidbits of his own. Vanessa and Chuck come to their friend's aid when Nate is once again forced to confront his father's abandonment. Finally, Eric discovers a secret that Bart has been keeping from Lily.
Title comes from the 1918 novel The Magnificent Ambersons.