In the Season 5 opener, Serena makes a grave error at her new job in Hollywood. Chuck and Nate then meet up with her in L.A., where Nate is captivated by an older woman (Elizabeth Hurley). Elsewhere, Blair is not pleased when Louis sides with his family over her; and Dan receives help from an unexpected source.
Nate gets a surprising offer from Diana. Meanwhile, Blair receives a visit from her future sister-in-law; Dan's quest to stop his book from being published has him seeking assistance from Chuck; and Serena compels Charlie to make a big decision.
Diana makes a request that tests Nate's ethics. Meanwhile, Serena and Charlie return home from L.A.; Dan uncovers who's publishing his book; and Chuck and Dan provide assistance to one another. Featured: scenes from a Jenny Packham fashion show.
Dan comes clean about his book to his friends and family. Meanwhile, problems arise for Blair after Louis reads Dan's book; and Diana uncovers some damaging info about one of Nate's pals and finds a way to benefit from it.
Discord erupts in Louis' family in the midst of a Yom Kippur celebration. Meanwhile, Serena's friendship with Dan may become a casualty of her new job; and Diana wants Nate to be her hero when problems arise with the launch of her new publication.
Blair has potential bridesmaids audition for the honor of being in her royal wedding. Meanwhile, Nate tries to make Diana jealous by getting close to Charlie; and Serena needs to secure the film rights to Dan's novel, despite being angry at him.
Several of the gang attend a production of "Sleep No More," an off-Broadway theater experience in which audience members wear masks. Meanwhile, Diana wants to use Serena to take down Gossip Girl; and Dan makes the rounds on his book tour.
Serena plans a wedding shower for Blair, complete with misleading info to keep Blair in the dark. Meanwhile, Chuck and Dan bond over not being on the shower guest list; and Nate and Serena are torn about giving Diana ammunition against Gossip Girl.
CeCe's family gathers for a Studio 54 party thrown in her honor. Elsewhere, Nate takes on bigger responsibilities at the Spectator, where his first lead story hits too close to home; and Blair seeks assistance from someone unexpected.
Blair's flashbacks reveal the fallout of her and Chuck's car accident, which Nate realizes may have been caused by foul play. Meanwhile, Lily gets a private eye to locate Charlie; and Vera Wang makes an appearance at Blair's bridal-dress fitting.
Amy Heckerling directs this episode in which Blair has a bachelorette party; Nate teams up with someone unexpected to gain more info about Blair and Chuck's car wreck; and Serena and Dan put on a charade of reigniting their relationship.
Dan discovers that a comedy group is performing excerpts from his book. Elsewhere, Blair attempts to salvage her friendship with Serena; and Ivy runs into the van der Woodsens as she heads out of town.
Chuck wants to express his gratitude to Jack for saving his life. Elsewhere, Blair and Dan's new romance hits a snag; Ivy gets unexpected assistance from William; and Nate is optimistic about landing a new investor for his newspaper.
Serena wants to pass her It-Girl torch to a hesitant Lola, whom she pressures to do a modeling gig at a lingerie show. Elsewhere, Chuck seeks Blair's guidance regarding his past; and Diana resurfaces and stirs things up at Nate's newspaper.
Blair and Dan go public as a couple by hosting a salon. Meanwhile, Lola gets to audition for a coveted role; Lily and Rufus clash over how to deal with Ivy; and Serena and Diana have a confrontation about secrets they don't want divulged.