Appropriately, shadows seem to appear throughout the entire series.
Shadows, Shadows, Everywhere Edit
Shadows of actors, boom microphones, cameras, and crew members often make unexpected appearances, as do the real thing. Look for them at most inopportune times and locations. They are frequently fleeting across faces, floors, and furniture.
Dark Shadows Revealed Edit
Although dark shadows were frequently revealed at unforeseen times and locations, the really Dark Shadows were never revealed and remain a mystery to this day.