A mission with Sloane nets Sydney a key piece of info on her past, as Sark spills the identity of his father's killer to the one person who would benefit most from Miss Bristow's arrest. Meanwhile, Vaughn and Lauren's marriage takes a major hit when she realizes that he's been keeping secrets and he sees that she's not above playing dirty to keep her man. Sark: David Anders. Lauren: Melissa George. Dixon: Carl Lumbly.