“All this technical medicine is long after my time. My father never did any blood work—they didn’t even know about typing blood in his day, let alone what they can do with it now. I suppose I was too bitter about not becoming a doctor to want to know anything.”

I puzzled over the entries a few more minutes, but this was work for Lotty. I stacked the books. Time for me to do something I could understand: I asked her how the intruders had gotten into the house.

“I presume Curtis let them in,” she said stiffly.

I leaned back in the chair and looked at her thoughtfully. Maybe no one had been in the house this afternoon. Maybe she was seizing the opportunity offered by her brother’s disappearance to avenge herself for his bungling their father’s practice all these years. Or perhaps in the confusion of the last few days she’d forgotten where she’d hidden the typed notes. She was, after all, nearly eighty.

I tried probing, but not very skillfully. She frowned ferociously.

“Young lady, please do not treat me like a senile old woman. I am in full possession of my faculties. I saw Curtis trying to burn his notes five days ago. I can even show you the spot where the wastebasket burned through to the carpet.

“Why he wanted to destroy them I have no idea. Nor why he should sneak in here to steal them. But both of these things occurred.”

My face felt a little hot. I got up and told her I’d check out the premises. She was still a little frosty, but she took me on a tour of the house. Although she said she’d tidied any disarray among her books and silver, she hadn’t vacuumed or dusted. After a painstaking search worthy of Sherlock Holmes, I did find traces of dried mud on the stairwell carpeting. I wasn’t sure what that proved, but I could easily believe it wouldn’t have come from Ms. Chigwell. None of the locks showed any sign of forcing.

I didn’t think she should stay the night here alone—anyone who came in once in such a way could easily return, with or without her brother. And if they had seen me arrive, they might easily come back to demand why in ways that an old lady—however tough she might be—would be unable to withstand.

“No one is forcing me from my home. I grew up in this house and I am not leaving it now.” She scowled at me fiercely.

I tried my best to dissuade her, but she was adamant. Either she was scared and didn’t want to admit it, or she knew why her brother was so desperate to get his hands on the notebooks. But then she wouldn’t have given the originals to me.

I shook my head in irritation. I was exhausted, my shoulders ached, my head was throbbing slightly where I’d been hit. If Ms. Chigwell wasn’t telling the truth, tonight wasn’t the night for me to figure it out—I needed to go to bed. As I was leaving, though, something else occurred to me.