In campaign mode, are the investigator decks reset prior to starting a new scenario, or do they carry over exactly as they were from the end of the just completed scenario (including cards that have been placed in your play area, cards in hand, in discard pile..)? Thanks in advance!

My understanding is that they are shuffled and reset. The only cards that will start in play are labeled "Permanent". The only changes to your deck are cards you have purchased with your XP, replacing or upgrading cards that were in the deck before. Each scenario is a new game aside from instructions you have received in the course of the campaign. You also start fresh with no damage or horror unless you accumulated mental or physical trauma.

Thank you, that's very helpful. That's my interpretation too. Just wanted to make sure I hadn't missed something. I didn't see that point covered in the rules so maybe they consider it too obvious to have to be stated..

The only changes to your deck are cards you have purchased with your XP, replacing or upgrading cards that were in the deck before. Each scenario is a new game aside from instructions you have received in the course of the campaign.

This might be implicit in the "instructions received in the course of the campaign, but it bears repeating: Any weaknesses that may have been added to your hand during a scenario also become a permanent part of your deck.

Thank you, that's very helpful. That's my interpretation too. Just wanted to make sure I hadn't missed something. I didn't see that point covered in the rules so maybe they consider it too obvious to have to be stated..

It is discussed in the Rules Reference, for what it's worth. Each new scenario in a campaign is considered a new game, so each time you reset the whole board, shuffle up your decks again, (apply Trauma, if any), (find your Permanent cards, if any), draw 5 cards, mulligan if you feel like it, and get 5 resources, and then follow the set up instructions for that scenario.

Also remember when purchasing cards, "Permanent" cards not only start in play, but do not count against deck size so if you purchase a permanent, you don't have to swap it out with anything.