Montana Smith said:Masks of Evil was the most problematic of the Young Indy TV series for me. Without Old Indy's bookends it really stands as the 'odd one out'. I enjoyed the unexpected excursion into horror and gore, but I'm caught between Lucas' original intention (the likely Halloween tale) and the presentation that we currently have.
If Indy really did face down Vlad, it had no obvious effect on his character in the following episodes. That would imply that the supernatural was an accepted part of his world, though it's not generally discussed or broadly acknowledged by the inhabitants of his world.
Indy, being an exceptionally open-minded individual, ready to accept that which cannot be denied, and ready to delve into the unknown, would be well prepared to deal with the supernatural. And, returning to the main topic, enabled himself and Marion to survive the Ark, by believing it possible to avoid the wrath of God simply by refusing to see it. (He had earlier believed in the magical invocation of Shiva in 1935, and it worked that time as well).
Well, the ending of Masks of Evil as stands makes it rather clear he (at the time) didn't really grasp what had happened and was in sort of disbelief. Given that he was back to the Front right after that, I doubt he thought about it much.
He experienced the things he did in ToD and still was a skeptic in Raiders, and even after experiencing the Ark, wasn't sure if the Grail existed in LC. He was pretty much throughout the main trilogy the eternal skeptic. Even in KOTCS he says, "There's always another explanation"--As in, a more mundane explanation. And I think that sentence is a perfect summation of his feelings past and present on the supernatural.
Just because Masks is the ''odd man out.'' doesn't mean it didn't happen. And given the exclusion of the Old Indy segments, plus the tie in segment with Istanbul, I think it's pretty clear that it DID happen. Why are Aliens, the Ark, Shiva and the Holy Grail believable in Indy, but Vampires are not?