Star Trek: Voyager: Season 6, Episode 4

6 - 4: Tinker, Tenor, Doctor, Spy

Stardate: Unknown. The Doctor programs himself with a subroutine allowing him to daydream, which puts him directly into the center of a crisis. An alien scavenger race called the Overlookers gains access to the Doctor's cognitive subroutines to make him their spy. But, the alien spy monitoring the Doctor's visions mistakes them for reality. When the alien raiders believe they have gathered enough information about Voyager, they plan to launch an attack.