Serena loves her new job in Hollywood, but makes a mistake trying to impress her boss. Chuck and Nate arrive in LA as their last stop of their Lost Summer trip, joining Serena at a glamorous party, where Nate meets a sexy older woman. Blair and Louis return from Monaco and begin planning their royal wedding, but when Louis refuse to support Blair's decisions against his family, their relation is at risk. A magazine is planning to run an excerpt of Dan's book until an unlikely ally helps him.