So.... We're going to start a Dark Heresy campaign soon, and I want to try and make sure I get the 'feel' and 'scale' of 40k right.

I was trying to figure out the Malleus elements to a campaign. What I want to make work is the idea - a classic one with the Ordo Malleus - that no-one is allowed to know they even exist - even other (lower ranking) members of the ordinary Inquisition; if you get caught up in a Malleus investigation, you get mindwiped or killed (depending on your usefulness and general spiritual resilliance). The idea that daemons are real, can physically manifest and that the dark gods are not just abstract theological concepts is something the Imperium will not, cannot, admit to its own people.

Now when you want to have a mission that they players have been involved in, you could always play it and then after the fact tell them "but you don't remember this anymore" but that seems a little weak. I'd rather have them figure out over time something's out of kilter - and that at least one of the somethings is them. Imagine that there has been one or more 'game sessions' that's happened where the players have been dragooned into service (as nearby Inquisitorial assets) by an Ordo Malleus Inquisitor (i.e. not their own Inquisitor). They've helped save the day, and in gratitude the Inquisitor has neatly sliced the whole incident out of their memory (with a few judicious alterations to patch over obvious stuff like injuries) rather than having them eliminated.

I was hoping for suggestions on things the players could find that might make them suspicious 'something is going on' (beyond the normal Dark Heresy 'something is always going on').

Ideas I've had:

• One player with Trade Armourer is likely to take responsibility for maintaining and modifying the party's (small) armoury of weapons. I was thinking that one week he'll realise that two of their shotguns are mars pattern weapons. Which is odd, because they were accatran pattern weapons when he locked them away a week before.
• A contact of the party disappears, and was last seen supposedly heading to talk to them. He never arrived, but definitely got off at the local transit rail station and left the plaza (the last time he appeared on a pict-capture), which is less than fifty metres up the street. There have been no reported road accidents, or murders, or violence in the area, and it was the middle of the day with the street full of traders and their customers.
• The sanctionaries are supposedly looking for a murderer who fits a (very vague) description of one of the acolytes, who was responsible for killing two sanctionate officers.

The ultimate aim is to get them to look into what's going on - and find evidence that a cult was hunted down and exterminated - along with all the witnesses and evidence - by....well.... them . And, ideally, by looking into it, that they'll find something that begins the threat anew - so they'll need to solve the problem all over; and getting the Ordo Malleus to intervene again (in the process convincing them to help solve the problem without either bombing the planet or executing the players!)

One image I wanted to put in was ultimately ending up in a crypt where an Inquisitor is supposed to be 'buried', and have the 'tomb' turn out to be a stasis casket where he is locked away for reasons he refuses to tell them.

Part of the inspiration was something I remember from the old Inquisitor game (or it might have been the Eisenhorn books & audiobooks that accompanied it) where one character in the background was musing on something called the Puritan's Dilemma:

This is what philosophers of the Holy Ordos call the Puritan's dilemma;

Imagine a threat to the Imperium. A subtle, secret threat. A fragment of dark lore, or perhaps a forgotten truth. One so dire, so inherently corruptive that it must be excised utterly. Not even the purest soul can know it without being tainted beyond redemption.

It is not enough that the heretics be hunted down or that the means by which they abused this secret be purged. Instead, it is necessary that even the memory that the secret existed in the first place - that there was ever anything to destroy - be erased from living memory. Every fragment of evidence, every witness, every rumour, all of it burned, buried and blotted out.

To achieve such a thing is not beyond the Inquisitor's authority. Kill enough people and any secret will die. But we fear the imperfection of our work. Imagine that despite the killings that somewhere, in the dark places beyond the Emperor's light, the secret endures. Imagine that, centuries from now, it will be found again and the threat born anew. And now no-one is watchful for its return, for no-one even knows that a threat ever existed to watch for it.

Who can be trusted to remember?

This is a very ambitious idea - one you'd really need the right group of players for. I reckon it could be absolutely amazing.

One more clue/bits of flavour off the top of my head:

- A warehouse, thought abandoned, burned down during the "missing" period. A number of bodies were found inside, but were quickly hustled off to the charnel houses. If the players are quick, they may be able to bribe/talk their way into one such house, finding that some of the bodies have obvious gunshot/melee weapon wounds.

Some additional ideas.

-wounds/bruises/ torn/bloody clothing that give no clue as how they appeared

-old notes / emails found relations to past conversations / clues that make no sense now

-odd cases of Deja Vu when a PC see something (an image on a vid screen / far off distant image / conversation of passerbyes that jogs a memory)

-doing a routine (like checking over a map of an unknown area / reaching for keys not hanging by the door) or knowing a number sequence / code word / phrase that they have no recollection of obtaining

-calling another PC by a name or nickname the other PC should not no or they have no idea why it sounds familiar

While reviewing several tedious hours of security pict-logs for his current investigation, a PC spots himself in a location he has no memory of visiting...

I like this idea, and it gives me a thought for a one-shot based on the ST:TNG episode "Clues," in which the crew is stunned and thinks they've woken up thirty seconds later. Until they start gathering clues that something's wrong, significantly more time has actually passed, and that android Data, who cannot be stunned, is lying about the incident. Heck, you could even found a party and campaign with it -- a bunch of people wake up to gradually discover that the Inquisition has mindwiped them. Once they work out what actually happened, the Inquisitor appears and offers them places in his retinue. Or, if it's a oneshot, kills them.