Star Trek: Voyager: Season 6, Episode 26

6 - 26: Unimatrix Zero, Part I

Seven of Nine is led to a place known as Unimatrix Zero, a place where Borg drones are individuals for a short period during their regeneration. However, once their regeneration is complete, all recollection of the event is erased. Captain Janeway uses this to form a plan of attack that would create a mutiny instilling independent thought from within the Borg Collective.