At the Snowflake dance, Blair and Chuck discover their lookalikes hooking up. Aaron's ex Lexi flirts with Dan, causing trouble with Serena. Nate, Jenny and Vanessa get into a messy love triangle that involves a stolen letter and a revealing dress. Bart Bass suffers a car accident on his way to the ball.

The entire Upper East Side of Manhattan is rocked when Bart Bass dies suddenly in a limo accident. Serena and Eric take the news very calmly while Lily has a troubling time despite her mother, Cece's, awkward attempts to comfort her. Chuck begins to blame Lily for his father's death and threatens to reveal a secret that Bart found on her before his accident. Meanwhile, Blair's mother, Eleanor, prepares for her latest marriage to Aaron's father Cyrus.

Serena enlists Charlie to go undercover Gossip Girl-style to determine why Dan and Blair are spending so much time together, and what role an unexpected visitor is playing in their lives. With Nate’s help, Raina decides to go on a search for her long-lost mother. Chuck’s hopes about his legacy are dashed with the reveal of devastating information from the past.

Blair’s dreams appear to be coming true, but Serena threatens to jeopardize it all by dredging up Blair’s past. Charlie befriends Vanessa, who may or may not have a hidden agenda. Nate is torn between his relationship with Raina and a truth he must keep hidden out of loyalty to Chuck.

Serena decides she is ready to relinquish the spotlight and sets out to make a reluctant Lola the next “It Girl” of the Upper East Side, starting with modeling at a Kiki de Montparnasse lingerie show. Meanwhile, Chuck reaches out to Blair or advice about his past, and Diana Payne’s return to The Spectator starts a power struggle with Nate.

Blair feels like her Upper East Side status might be slipping away and devises a plan to assure that doesn’t happen. Meanwhile, Lily throws a family gathering – including William, Carol and Lola – in an attempt to prove the van der Woodsen family is as united as ever. Finally, Nate digs into Diana’s past and is surprised by what he discovers.

Blair enlists Serena to be her stand-in at an important meeting when Blair finds herself needing to be in two places at the same time. Meanwhile, Ivy and Lola team up to help Chuck with a personal vendetta, and Nate makes a decision about the future with Diana Payne.