Susie Misner

While investigating a mystifying incident at Massive Dynamic, Olivia seeks to rid her consciousness of Agent Scott and Peter's past catches up with him. Also available on iTunes

When Blair s father, Harold (recurring guest star JOHN SHEA), comes home for the holidays with an unexpected guest -- his boyfriend, Roman (guest star WILLIAM ABADIE - 'Entourage,' 'The O.C.,' 'The Pink Panther') -- Blair finds it difficult to hide her disappointment and hatches a plan to get rid of Roman for good. Meanwhile, Jenny and Vanessa (recurring guest star JESSICA SZOHR) help Serena plan the best Christmas surprise ever for Dan; Dan, in turn, may be thinking of his own surprise for Serena. And when Chuck texts Blair from Monaco saying that Nate has joined him there, Blair worries that Chuck may disclose the details of their hook-up. Back in Brooklyn, Rufus refuses to remain the understanding husband after a former lover of Alison's (recurring guest star SUSAN MISNER) calls the house. Also available on iTunes and VUDU

Serena has absolutely no intention of attending the upcoming Debutante Ball, until her grandmother, CeCe (guest star CAROLINE LAGERFELT - 'All the King's Men,' 'Nash Bridges'), announces that Serena must attend. Unfortunately, CeCe does not find Dan to be the 'suitable escort' she had in mind for Serena, and makes her opinion heard loud and clear, causing a riff between Serena and Dan. Blair and Nate, now officially broken up, decide to go to the ball together as friends; however, Nate becomes jealous when he begins to suspect that Blair may already be seeing someone else. Meanwhile, Jenny finds herself torn between attending her mother s (recurring guest star SUSAN MISNER) art opening or following her dreams of going to the Debutante Ball, even though the latter is against her parents wishes. And Rufus finally learns the real reason Lily broke up with him all those years ago. Also available on iTunes and VUDU

When Dan finds out that Serena and her family are celebrating Thanksgiving alone, he naively invites them to spend the holiday with his family, creating an uncomfortable situation for Rufus and Lily.