Maybe instead of the Inquisitor bring in a NPC the players can relate to and trust then it turns out their being led to their doom in order to make the "Champion" of Chaos stronger. Thats a plot twist.

I always liked the idea I came up with for a Call of Cthulhu campaign, but that can easily be adapted for DH:

A cult (most likely a Tzeentch cult) needs a human sacrifice for the summoning of a greater daemon. The catch is, that the sacrifice has to be sacrificed in the moment it realizes that it is to be sacrificed and can do nothing to stop or do against it. So the cult deliberatly helps the acolytes to uncover the mystery and gives them informations about themself (using a messanger, or trusted NPC) to prepare them as sacrifices. They plan to lure them to the altar, reveal the truth to them and kill them as sacrifice.

I like! That can be very dramatic for the players and the characters, kinda of a your right on the edge of the cliff. So the Acolytes need to discover the cults plans before they become sacrificed or have to figure out how to get out of a very tight spot and a hard place.

Just a thought but the Inquisitor could know this is occurring and tries to save his acolytes or he is using his own acolytes to sacrifice in order to summon a greater daemon or turn himself into a Daemon Prince.