Introductions.
"Good." for the first time, Pearl's smile reached her eyes. "What I am about to tell you is Sealed to the Ordos, you may not discuss it with anyone outside this room. Because Guardsmen. Noob Guardsmen. Twenty thousand heavily armed First Founding brand new Guardsmen on this ship. Panic bad."
She paused, taking a breath. "Damn, I haven't told you why they might panic have I? Making a hash of this. Mm, cover broken, silly dress can go." She strips her dress over her head to reveal a flesh-toned (exactly her flesh toned) body glove, handing it to the muscular woman. "That's better. Silly dress gone, now I can think."
"Okay, start at the beginning. Four jumps ago, fluctuation in the Geller field, something comes through. Not serious, just one of those things that make space travel such an unremitting joy. Ships Chaplain does and extra exorcism, Enginseers anoint more anointy-bits, problem solved. Demons can't survive in real-space after all. Except that it wasn't. After the next jump, ship is off course. More exorcisy, more anointy, armsman patrols. Next jump, even more off course. Many many hoops jumped, Captain reverses course. Doesn't work, even further off course. Bridge Officer, Lieutenant Wilks, takes ships Chaplain, ships Psyker, company of Armsmen, heads off to find and eliminate problem. None come back."
"Captain screams for help, Inquisitor Varsh sends Fetch to me, all available Inquisition assets" She waves one finger in a circle "That's us, seconded to task as Activated Cell Seven Four. Welcome to the cell, we have a demon or at least a demonish thingie to hunt. We know that it is clever because dumb one would not last past a few seconds, that it can alter the course of the ship, that it is based somewhere around Engeneerium Deck 4B, and that it ate 120 well-led and supported men without burping."
"Any questions?"