S6, E12: When Liv (recurring guest star Penelope Mitchell) and Luke’s (recurring guest star Chris Brochu) father arrives to town to celebrate their birthday, they try and convince him to let Jo (guest star Jodi Lyn O’Keefe) and Kai (recurring guest star Chris Wood) take their place in the merge ceremony. After Tyler finds out that the merge is happening sooner than he expected, he urges Liv to let him talk to her father. Meanwhile, after Caroline’s plan to cure her mother takes an unexpected and devastating turn, Elena, Stefan and Damon gather at the hospital, while Jo attempts to save Sheriff Forbes’ (recurring guest star Marguerite MacIntyre) life. Lastly, with the merge set to take place, Damon’s risky plan quickly sends things spiraling out of control, forcing one of the twins to take matters into their own hands.