1 Charon: The River Mnemosyne. Drink from it to recover your memories.
2 Adam: What will it do to us?
2 Charon: Restore your memories. Drink.
3 Jamie: What will it do to us?
3 Charon: Your memory will return. Now drink.
4 Adam: What will it do to us?
4 Charon: Just drink already!

And so we move into Irregular Webcomic! strip numbers that look like years following the end of World War II. This is the first number that's really hit me as "this could be a year".

Things that happened after WWII, although I wasn't actually around for many of them, are at least represented enough in contemporary film and television that they seem almost familiar. Things before WWII have that strange aura of non-reality that comes from not being able to experience any of it in quite the same way.

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2019-03-17 Rerun commentary: One presumes that the magical properties of the waters of all these various underworld rivers are not carried by the water as it flows from one river to another, or to various seas and oceans. Or else any random glass of water form any body on Earth would be a mixture of all of the different river waters, and have multiple mutually contradictory properties. Thus we must conclude that the magical properties of the rivers are the result of the geography, and not an inherent property of the water itself.

Water that is running between the banks of the River Mnemosyne restores memory, while the same water, if it were running between the banks of the River Lethe, would remove memories. The magic must be inherent to the river banks, not to the water flowing between them.

Yep, logical analysis applied to mythology. What can't it do?