Credit: Eric Liebowitz /The CW

After their plan to break into the school for a late night, booze-fueled pool party takes a tragic turn, everyone’s favorite Upper East Siders find themselves in a bind: Turn in the key-holding party mastermind or face mass expulsion from their preppy Manhattan high school. Chuck, Nate, Serena, Blair and a very skeptical Dan make a pact to keep quiet but the school’s new headmistress is on a mission to find the culprit.

In the midst of the crisis, Nate’s doing everything he can to win back Blair, including admitting his undying love and, when that doesn’t work, confessing to the crime at hand in order to protect her. B’s touched but with Chuck still holding their hookup over her head she’s not about to give in — especially after Dan’s friend Vanessa catches the illicit couple rehashing their sex and lies on videotape. Bribery ensues, but ultimately V hands the evidence over to B, who pays her rent for a year in return. (But only so she can wipe the slate clean and go back to hating her. She is a Waldorf after all.)

In the end, Nate gets suspended for lying about the key but he also gets his girl back — and an “I love you too” in return.

So who’s the real troublemaker? It’s Serena who had the key that unlocked the school — a remnant of wild past and a few dates with the captain of the swim team. Eventually, the reformed party girl gives a believable confession in order to protect Dan, who could lose his scholarship if he gets expelled, and gets a light slap on the wrist.

On the parental front: Rufus has a confession of his own: he’s still in love with Lily and begs her to give them another try. She ultimately agrees to run away with him for the weekend but after Serena realizes the plan, she pleads with her mom to reconsider for her and Dan’s sake. “I’d rather be Chuck’s stepsister than Dan’s,” she tells her mother, who ultimately accepts Bart Bass’s merger — er, marriage proposal. You know what that means! Chuck will be S’s new stepbrother. Be careful what you wish for! –Carolyn Butler

Photo: Eric Liebowitz /The CW