I finally understand it. There's a part of Hypatia that she doesn't even know about. It's always there, riding along in her mind. Takes over, and forces her to use more of the original serum, with some regularity. The Duke keeps her here. And - if I'm right - sends her out on diabolical assignments. Hypatia is the one the newspapers are calling the the Crown Killer. She leaves, and comes back leaving bloody footprints. But there's a cure, a counter-serum. I'll try to administer it, once I get my notes from the safe in Disease Treatment.
Hello? Oh, Alexandria. I was just. No! It's you.
Yes, Vasco, my love. You're found out. And now we have some experiments to conduct. Come, I'll make you comfortable.