There was one lone survivor of a cult massacre led by an infamous Arch-Heretic whom the Inquisition has been hunting for decades, but have had no success because he never leaves any witnesses. The Acolytes are sent to transport this witness back to the Tricorn where the Inquisition's psykers can extract an image of the Arch-Heretic (Kolos The Executioner?) from his mind and thus Dowse his location. Naturally, the Arch-Heretic sends wave after wave of nasty surprises to prevent the Acolytes from delivering their 'cargo'.
An outbreak of warp activity has been traced back to a mysterious drug that activates latent psychic abilities. The Acolytes are sent to infiltrate the local criminal underground to locate the supplier (possibly xenos?) of this strange new drug.
On a sparsely populated Frontier world, settlements are being attacked by a man with seemingly supernatural powers. Assuming he is either a psyker or mutant, the Acolytes are sent to put an end to his rampages. It turns out, he is niether a psyker or a mutant, but a farmer who found a Halo device while tilling his field and has been taken over by its power. If your players are anything like mine, this will lead to an interesting... discussion about who gets to keep the artifact...
Sent to investigate reports of a warp entity in an Imperial bascillica, the Acolytes eventually discover that the entity is the 'ghost' of an Imperial official who is frantically trying to warn people that he has been assassinated and replaced by a doppleganger with sinister plans.