THURSDAY, OCTOBER 17

THE VAMPIRE DIARIES - (8:00-9:00 p.m. ET)

"Original Sin" (Content Rating TBD) (HDTV)

SECRETS OF THE PAST - When Elena (Nina Dobrev) and Katherine (Nina Dobrev) have the same dream that Stefan (Paul Wesley) is in danger and desperately needs their help, they convince Damon (Ian Somerhalder) to help them find Stefan. However, their plans are thwarted by a mysterious young woman named Tessa (guest star Janina Gavankar) who seems to know everything about Stefan's history. In flashbacks to a distant time and place, Tessa reveals the shocking secrets in her past and what she has planned for the future. She also has a disturbing message for Damon about his own future. Silas (Paul Wesley) forces an unwilling accomplice to help him search for Katherine, leading to a confusing and life-threatening situation for Matt (Zach Roerig). Finally, Silas reveals the reason he's determined to find Katherine, and Damon and Elena face a disturbing new reality. Jesse Warn directed the episode written by Melinda Hsu Taylor & Rebecca Sonnenshine (#503).