After a three week hiatus, anticipation was high for this week's "Supernatural" -- not least because it featured the return of Bobby (Jim Beaver), who met an untimely end eight episodes previously in "Death's Door." The show was operating on two levels with "Of Grave Importance," one being the Monster-of-the-Week case of the spooky Van Ness House, the other being Bobby's ghostly return and the Winchesters' discovery of that fact. Though the two story threads spent a great deal of time intersecting, only one of them really worked for me: the reintroduction of Bobby and Sam and Dean's subsequent reactions to his ghost status.
What initially appeared to be a typically humorous, filler episode of Supernatural actually gave us some big developments on the mythology side of the show, as one of the leviathans dropped their master plan on Sam and Dean at the end of the episode. So what do these ancient, terrifying, people-eating monsters want to do now that they're out of their cage?