Violent attacks happen on Voyager's Maquis crew.
Several former Maquis crew members are found unconscious after being attacked, and Tuvok investigates. Evidence suggests an attacker with access to security protocols, and the culprit turns out to be Tuvok himself, who has no memory of the attacks.
The Bajoran Teero Anaydis, a former Maquis who experimented with mind control, had planted a trigger in Tuvok's mind years earlier and activated it through a message sent to Voyager from the Alpha Quadrant. The attacks were meant to awaken the victims' Maquis loyalties so they would take over the ship. With Janeway's help Tuvok regains control of himself, and he uses mind-melds to restore the others and recover Voyager.