Tuvok faces a perplexing situation with vivid, emotional visions of a young girl falling from a precipice, a stark contrast to his Vulcan demeanor. The crew's discovery of a gaseous anomaly containing siriillium, an energy source, leads to a plan to stockpile it, affecting Neelix's pantry. A mind meld between Janeway and Tuvok reveals his memories on the Excelsior, including a tense moment with Captain Sulu during a mission involving the Klingons. The meld uncovers a virus mimicking memory engrams, causing Tuvok's distress. The virus, thriving on brain peptides and disguised as a traumatic memory, is eradicated with thoron radiation, resolving Tuvok's crisis.