SPOILER INDEED!!!! Keep your noses out Players or you spoil your own fun!
It's a new plot using different NPC's.
There are nods to the old plot and the cults involved, Purple Hand, Red Crown, but locations/adventure events are different. It mentions that the groups above were frustrated in a plan some years ago by a group of heros - e.g., without delving into it if you want to say the original adventure happened in the past you can - though perhaps not through to the Empire in Flames parts.
I am digesting and figuring out the "big moments". One is - the play may end very badly (and we're not just talking about reviews). There's another that is more "emotional" which is not "on the page" but pretty much called for (people you met went missing, at least one of them being likeable and sweet, and now you find what's left of them - well that is tragic and calls for a Stressful check in my book). The finale scenes are intended to be huge/over the top as well - epic fights.
I need to read it again, couple of times really - it's well integrated across its chapters (unlike some earlier edition campaigns) so that NPC X turns up here, here and here etc. (as GM you want to know that plan first time they appear). There are some bits that may be a bit complex to run (parallel events unfolding). That happens "just a bit" in first part and "a whole lot more later on" (perhaps so GM and group get hang of it).
Interesting points (well interested me):
The Emperor makes an appearnce (you get a card and actions for him and in passing learn he does have a son, Luitpold - there's a blast from the past - doesn't factor in adventure though).
Surtha Lenk appears off stage and indeed Wolfenburg is not a healthy place to live in any edition it seems. We stop short of Archaeon appearing but "that storyline is not invalidated".
For those who follow the wargame version, a Luminark appears (who says Light wizards are not use in a battle).
The high level epilogue has Chaos Waste rules for the not-faint-of-heart.
There's a trip to Middenheim and the Sacred Flame - Dr. von Oppenheimer has a plan (is it a surprise to say it ends explosively?)
Some GM-comforting canon on warpstone confirmed (it's very very very hard to dispose of the stuff - oh we're in spoiler territory let's be clear - it's confirmed the silly humans think they can at times but the high elves aren't even sure of how to).
My Thoughts of Tinkering:
I don't think plot line needs it. Unlike gathering storm (schulmann is just way too obvious, come on!) this one has any number of suspects any no more likely or tragic a choice for the villain.
I think my prep work will be just fleshing out what it provides and doing table top aids to help it in play. For example it starts with investigation in a district of city sort of like the Winds of Magic adventure in Altdorf and I will probably use similar approach as I did there of creating little cards with the descriptions of the neighbourhood NPCs to scatter on table so heroes choose who to go up to and chat.
The fact villain is "tragic" is mentioned in a sense and something that can be developed and that means they can be presented sympathetically earlier on before their villainy is revealed. Very much like your typical Batman villain (by the end they are very probably best played like your typical Batman villain). This applies whichever of the candidates you select for villain. There are a lot of "flawed but struggling to do right thing as they see it and admirable in their way" people of whom one turns out to be "really flawed with a very bad idea of right thing".
The "great conspircacy" , which the vilain is leading-twisting, can really be seen as a simply bourgeois class chaffing at the Empire's restrictive nobility and official cults and wanting more liberty and freedom. It's very easy to see it (like the secret societies Lure of Power introduced) having lots of "unIlluminated members" who support it'. Its ideas can presented in a way that is "friendly to a 21st Century view of things". There are a couple of secret societies from Lure of Power that would make sense to reflect it (the campaign does use not that concept/those cards). I definitely won't have it be calling itself, "The Great Conspiracy".