KLAUS' PAST COMES BACK TO HAUNT HIM — As the war among the sire lines continues to grow, Klaus receives an unexpected visit by a figure from his past. When Elijah suspects that Tristan is hiding something, he enlists Marcel's help to find out what he's up to. Elsewhere, Davina struggles with her role as Regent and seeks advice from Hayley. Finally, an ancient secret that is uncovered threatens to tear the Mikaelson brothers apart for good.