Hello again. I'm on day 8 of Haruspicus now and ran into something that's freaking me out. I'm doing the quest to pin the blame on one of the Vlads and was directed over to Catherina's house. She and her husband are infected! Did I do something wrong? I thought I only had control of whether MY adherents live or die. Is there anything I can do? I don't want to screw myself out of the good ending.

Don't worry - other's Adherents fall ill from time to time. If you didn't waste panacea and found enough "powders", you can cure all the Adherents in game. (Which brings you to an even better ending, than if you'd only save yours ) Until then, make sure to keep them alive with antibiotics. Good luck.