In The Vampire Diaries Season 4, Episode 22, “The Walking Dead," ghosts return to Mystic Falls, some looking for revenge. First, Caroline tries to make Elena mail out her graduation announcements, but she's obsessed with another project. Sheriff Forbes asks Damon andStefan to investigate who's been harming hospital patients. Katherine doesn't want to help Bonnie, who needs the doppelganger’s help to defeat Silas. Matt and Rebekah are around, too. Read the full recap here.