In the Kennels you find a note talking about a loot cache in the incinerator room. You get some weird clues that didn’t really make any sense to me. This guide explains how to open the door to the cell in which the book is you need and how to extract the code from the clues.
There is a video containing a visual version of this guide at the end of this guide.
I strongly suggest you take out all the enemies in this area before you start worrying about the loot cache.
The lever you need to pull has no lever in it. There is a lever in a nearby cell:
Take it up to the 3 levers in the left part of the Kennel and it will automatically be inserted. You only have to pull that lever, but pulling the others will release some hounds that kill some of the guards around the place.
The note talks about 3 clues that you are supposed to look for in your strictures. That is actually the title of the book that you find in the cell you just opened:
The code is 217, matching the words in the note to the numeric values next to the words in the book. Go up to the door at the start of the left room of the Kennels and change the code to the left of the door:
When you open the door some rats will come out of the room. There is enough of them that they actually attack you, so after you open the door quickly find some high ground so they can’t reach you. After the rats have gone go into the room. Where the hounds are lying on top of some rubble you will find some consumables.