Devastated by the current state of her relationship with Nate and still dealing with the guilt from her recent indiscretion, Blair puts on a happy face for her 17th birthday party and attempts to hide the truth from her friends. Hoping to ease the tension between Serena and Vanessa, Dan takes Vanessa to Blair's party so the girls can have some bonding time, but this only ends up making Serena more uncomfortable. Jenny brings her mom (guest star Susan Misner) home for a surprise visit, but Rufus may not be ready to forgive and forget. Nate's parents (guest stars Sam Robards and Francie Swift) ask him to make a huge sacrifice in an effort to salvage his father's business as he faces charges of embezzlement and fraud.
Title comes from the 1984 film Sixteen Candles.