Star Trek: Voyager

Unimatrix Zero (1) (6x26)

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Seven of Nine is led to a place known as Unimatrix Zero; a place where Borg drones are individuals for a short period of time 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 from within the Collective.