S4, E20: Acting on a mysterious tip that a plot is brewing against him in New Orleans, Klaus makes a trip to the town he and his family helped build. Klaus’ questions lead him to a reunion with his former protégé, Marcel (guest star Charles Michael Davis – Grey’s Anatomy, The Game, Switched at Birth), a charismatic vampire who has total control over the human and supernatural inhabitants of New Orleans. Determined to help his brother find redemption, Elijah (recurring guest star Daniel Gillies) follows Klaus and soon learns that Hayley (recurring guest star Phoebe Tonkin) has also come to the French Quarter searching for clues to her family history, and has fallen into the hands of a powerful witch named Sophie (guest star Daniella Pineda – Homeland). Meanwhile, in Mystic Falls, Damon and Stefan continue with their plan for Elena, while Katherine reveals a surprising vulnerability to Rebekah (recurring guest star Claire Holt) and asks her to deliver a message.