“As a doctor, you know that there were no scientific tests for poison till the mid-nineteenth century. Maybe one of the reasons why arsenic was so popular is that the symptoms of arsenic poisoning are identical with those of certain gastrointestinal disorders. I read that in the same book that told me arsenic remains in the body—in the roots of the hair and under the nails—for an indefinite period of time. That’s why I thought we might have luck tonight.”

“I have never heard of it after so long a time,” said Blankenhagen. “But perhaps no one ever tried. Murders several hundred years old are not generally of interest to criminologists.”

“Get on with it,” said Tony, nudging me.

“The other night I just happened to find myself in Burckhardt’s room.”

“I knew it,” said Tony. “I knew it…. We’ll discuss that later. I suppose you tripped and fell and accidentally, not meaning to do any real searching, discovered a secret panel?”

“I found a box,” I said haughtily, “which contained a quantity of grayish powder. I didn’t think of arsenic at first. The color put me off, for one thing. I think of arsenic, when I think of it at all, as white. Either the stuff was contaminated by dust and dirt, or it had been colored, as commercial arsenic is, to keep people from mistaking it for salt or sugar.”

Blankenhagen interrupted.

“What you found may not be arsenious oxide, the ‘white arsenic’ of popular fiction. Elementary arsenic is gray, metallic in structure. Upon exposure to air it takes on a darker color and loses its luster.”

“You can look at it later, if you want to. It’s not important; most forms of arsenic are intensely toxic. It was not the color of the powder that alerted me. It was something else altogether.

“The hidden drawer where I found the box was littered with the bones of dead rats. They had gnawed their way into the box, and—curiosity killed a rat. Defunct rodents aren’t unusual, but it was extraordinary that so many of them should have chosen the hidden drawer as a place in which to die.

“Dead rats…rat poison…arsenic…the witchcraft-poison complex. I guess that was the way my thoughts ran, but I wasn’t aware of the progression; it just seemed to hit me all at once. And with that came another thought. What if we had been looking at the tragedy of Count Burckhardt and his wife backward? What if he was not the villain but the victim of a plot?

“My first reaction was a violent negative. But the more I thought about this new theory, the more things it explained. My assumption of Konstanze’s innocence wasn’t logical. It was based on a number of emotional prejudices which I needn’t go into in detail.”

Tony snickered. I took the golden amulet from my pocket and handed it to him.