I'm aware this has probably been discussed to death elsewhere, but I'm fairly new around these parts, so bear with me. The character of Valtane, who first appeared in Star Trek VI: The Undiscovered Country
, reappeared in the VOY episode "Flashback", which depicted additional events during that movie. In the TV episode, Valtane dies before the USS Excelsior gets to Khitomer, but as everyone knows, he appeared alive and well on the bridge of the Excelsior at the end of TUC, after the battle of Khitomer. Now I've heard a lot of theories trying to reconcile this - Valtane has a twin brother, he recovered in sickbay, Tuvok's memory was faulty - and none of them really click for me. Valtane looks a bit too well to have recovered in sickbay at the end of TUC - I'd imagine he'd probably be recuperating for a while, not going straight back on the bridge, minus even any scars - and besides, the clear implication of the TV episode was that Valtane died, and that was the reason the virus left his body and transferred itself to Tuvok. And why would Tuvok's memory specifically home in on this time period if it wasn't when he caught the virus?