In early 2376, in [#126 Riddles], Tuvok is attacked by a cloaked lifeform in the aft compartment of the Delta Flyer.

As Tuvok and Neelix return in the Delta Flyer from a diplomatic mission, Tuvok investigates the aft compartment. As he uses a tricorder, he is attacked by an unknown cloaked lifeform. The attack renders him comatose and he is taken to Voyager's sickbay.

in the Delta Flyer's aft compartment, a cloaked lifeform fires at Tuvok who is pointing a tricorder in its direction

Neelix in the cockpit of the Delta Flyer

aerial view of Neelix bending over the injured Tuvok in the aft compartment of the Delta Flyer

Naroq (pictured), a security official of the Kesat species, is very interested in the attack: legend has it that the Ba'Neth (in Kesat "shadow people") assess alien technology while cloaked because they are obsessed with hiding their identity. Naroq is allowed to work in the Delta Flyer, and looks for veridium isotopes which are present in residual particles from the Ba'Neth's cloaking fields. Since veridium has a very brief half-life of less than seventy hours, Naroq has never before been able to get readings as good as the ones he finds on the Delta Flyer. Naroq uses a photolitic converter he has devised to illuminate the particles and reveal the alien's appearance - they are multipeds (with tentacles) (pictured). The crew deploy Voyager's deflector array the same way and thereby uncloak a fleet of Ba'Neth ships surrounding them. The aliens begin to fire when they are hailed and manage to flee in an ensuing chase. Meanwhile, Tuvok regains consciousness. His neural pathways have bypassed the damaged tissue but this creates new synaptic connections so that his brain "rewrites" itself, resulting in the loss of what it means to be Vulcan (logic etc.). When Naroq questions him about the cloaking frequency on his tricorder which he saw in the instant he was attacked, Tuvok has a flashback but cannot remember any details. Helped by Neelix, Tuvok begins to have fun and finds he enjoys baking desserts. When Janeway questions him again about the cloaking frequency, Tuvok cannot find the words to express what he saw and instead draws it out in icing on his latest cake creation. The Voyager crew are thus able to locate the hidden spacefaring civilisation of the Ba'Neth. Naroq generously gives the Ba'Neth his photolitic converter in exchange for information about the Ba'Neth weapon, which is needed so that the Doctor can devise treatment for Tuvok's mental condition.

Behind-the-scenes: Roxann Dawson on directing [#126 Riddles]
(Roxann Dawson also plays ensemble cast character Torres)