So here's my plight: I need to figure out how much of a plot to reveal to my players - and when to do it.

'm planning a D&D campaign. In this, the plot is simple: A portal has been opened from another plane of existance, and the denizens of that plane have made a Consulate in the capitol of the nation of ... well, Godmondia for now.

Many years later, in a province of Godmondia, the regional capitol is getting it's own Consulate - an opportunity for trade and great profit.

Now.

The otherworldly denizens are thoroughly evil mindcontrolling monsters. The money they pay for stuff is meaningless to them, and with every trade deal comes creeping mind control. This is the plot: Figure out the Consulate are evil, destroy them locally, take back the capitol. Do I try to obfuscate this? Or do I make it pretty plain that this is what's going on? 

How would you do this? I'm leaning towards describing the succes and wealth of the capitol - how happy the populace are - and frankly I think that'll be more than enough. After all, it's an RPG, right? Everyone knows there's a plot. 

But there is the risk of the players ... actually missing it. Am I underestimating them?

Never assume the party will do what you want and/or guess what is going on.

The PCs will not have your context, so how do they determine that NPCs are mind controlled?   To them that is just how they act.  Just because they know there is a plot, does not mean they understand your plot.  Their plot will be about something 100% totally different.

Do you obfuscate this plot?  not in the beginning.  The PCs have to have the context that your plot is conceivable, let alone occurring.  For example get them to see this plot via some sort of history book/papers that in the past it has occurred before.

We come from a world that money has meaning.   So how do PCs understand,  "The money they pay for stuff is meaningless to them"?   

How do the PCs actually determine, "with every trade deal comes creeping mind control. "  These are two points that PCs will probably not gravitate too.

Without understanding those two points above, it is unclear how the PCs can, "Figure out the Consulate are evil, destroy them locally, take back the capitol. "

But there is the risk of the players ... actually missing it. Am I underestimating them?

I'm currently DMing a plot about Ragnarok, and my players have just used Commune to ask a god whether they should free Jormungandr or whether this will cause destruction of the world and mass death of people. Do not assume your players will figure out what is going on unless you shove it right in their face.

I’d keep it a secret at first. Maybe someone figures it out, and that can be very satisfying as a player. 
But as a back up, if they don’t, the party can always find some incriminating documents on a collaborator. 

Yeah, I agree with Xalthu. As a player, it's fun to unveil plots, but then again, it's not very easy. Depends on how complicated the mystery might be -- if they're not figuring it out, just throw something out there that'll make it all easy. If you want the campaign to move faster, without a lot of who's-the-murderer-in-the-cloak stuff, then make it plain and easy. I would say, though, for a more compelling storyline, why not make it a fun little plot for the characters to unravel piece by piece? (Maybe I'm just a stickler for mysteries) So, yeah. Depends on how intricate you want the campaign to be, and on how good at problem-solving your players are.

So the consensus is that there's no consensus. Well, I suppose that's hardly surprising. 

I think my players are clever enough to figure it out. It's not that. It's propably more that I'm not great at limiting information. Hm, it's like this: If I give a bunch of information about the world, it's characters, politics, factions and so on - and most of that is basically irrelevant for this particular problem ... that's good world building, but the relevant information get's obscured by lots of information that's not relevant, for this particular thing.

So in a way I'm the weakest link. 

Anyways, good input from everybody. No closer to an actual solution though.

It shouldn't be too hard to just state that ... yea, they're wealthy and happy in the capitol, but population has been declining for no readily apparent reason, even with all the influx because they're so happy and wealthy. 

That should be enough to be heard through the noise, right?

Here's how I do it (i'm prepping to run my next campaign, so I'm in the process of doing this now).

I make a list of sorts. I number that list with each level that I expect the characters to reach. Then I start assigning 'reveals' to each of those levels. It could look something like this:

1 - Blissfully unaware of the plot
3 - Realize that folks who trade regularly with the extra-planar people don't act in the best interest of their own people, perhaps they are being bribed or are just greedy?
5 - Learn that the extra-planar folk have psionic/magic abilities like charm person, suggestion, dominate, etc. (perhaps when the PCs start to become an irritation, the baddies try to 'persuade' the PCs to get with the program, and thus reveal their mind control abilities in the attempt)
7 - After having direct contact with some of those being controlled, come to realization that this is mind control and that this is a larger plot infecting many powerful people
9 - Figure out just how far the corruption has gone
11 - start actively trying to undo that corruption (openly fighting the extra-planar folks)

Obviously this is just an example. But in each case, if the PCs haven't figured out stuff on their own, then at those levels something will happen to GIVE the PCs the info. Drop hints, and if they pick up on those hints and figure it out before then - great. But know that players tend to pick up on only 1 hint out of every 100 you drop (varies depending on the group). If they reach the designated level without having seen thru your obfuscation, then you 'arrange' for them to get the info (find a document, have an NPC tell it to them, overhear a conversation, whatever it takes).

The PCs will still think that 'they' figured it out on their own, sit back and congratulate them for doing it (even though you know that they weren't even close to figuring it out, and that you had to spoon feed it to them - congrats this is now your own private joke).

The big problem with mysteries in TTRPGs is that the players have extremely limited information; they only know what the DM tells them, so unless you're in habit of throwing mountains of red herrings at them, they'll figure everything you actually tell them is important, so either they have enough information to solve the mystery (and solving it is easy), or they don't (and solving it is impossible).

Your particular scenario is close enough to a standard villainous trope that, if you bother to tell the players about it, they'll probably assume it's an evil scheme.

In my experience, you really have to make it blatant before you're sure the players will get it.

For mind control, the players probably need to experience it second-hand to notice it.

I'd suggest having them start out with a mentor/employer figure, doing more normal D&D stuff (this also means that you're not thrusting them into big plot immediately, which is usually better, anyway).

And then, the mentor figure starts behaving weird. And has a new ally who's always there, and who gets consulted a lot.

And the nature of the jobs changes...

Quote from HarmAssassin >>

Here's how I do it (i'm prepping to run my next campaign, so I'm in the process of doing this now).

I make a list of sorts. I number that list with each level that I expect the characters to reach. Then I start assigning 'reveals' to each of those levels. It could look something like this:

1 - Blissfully unaware of the plot
3 - Realize that folks who trade regularly with the extra-planar people don't act in the best interest of their own people, perhaps they are being bribed or are just greedy?
5 - Learn that the extra-planar folk have psionic/magic abilities like charm person, suggestion, dominate, etc. (perhaps when the PCs start to become an irritation, the baddies try to 'persuade' the PCs to get with the program, and thus reveal their mind control abilities in the attempt)
7 - After having direct contact with some of those being controlled, come to realization that this is mind control and that this is a larger plot infecting many powerful people
9 - Figure out just how far the corruption has gone
11 - start actively trying to undo that corruption (openly fighting the extra-planar folks)

Obviously this is just an example. But in each case, if the PCs haven't figured out stuff on their own, then at those levels something will happen to GIVE the PCs the info. Drop hints, and if they pick up on those hints and figure it out before then - great. But know that players tend to pick up on only 1 hint out of every 100 you drop (varies depending on the group). If they reach the designated level without having seen thru your obfuscation, then you 'arrange' for them to get the info (find a document, have an NPC tell it to them, overhear a conversation, whatever it takes).

The PCs will still think that 'they' figured it out on their own, sit back and congratulate them for doing it (even though you know that they weren't even close to figuring it out, and that you had to spoon feed it to them - congrats this is now your own private joke).

 Hm. This is remarkably good, not least because this is something that would work for me. 

Thankfully my players are highly suspicious of how I think, so that always helps them figure out what the plot is. But having an escalation ladder is a pretty neat tool for this, thanks =)