“Nonsense,” Julia said. “We have all day today, and tonight if need be. That’s plenty of time.”
“So, what have we learned?”
“I’ve conferred with a number of scholars here in Rome,” Callista said, “and several of them have lent me their relevant books.” She gestured to the heaps of papyrus leaves and scrolls that overloaded her desks and tables. She took up a tiny scroll and held it like a trophy. “This one proved to be extremely important.”
“How so?”
“It’s from the collection of Xenophanes of Thebes. He is the architect who designed Pompey’s theater complex on the Campus Martius. Being an architect, he is an avid scholar of geometry. This book is by a Pythagorean philosopher named Aristobulus.”
“I’ve met Pythagoreans,” I told her. “There are even a few senators who follow that sect. They are very boring people, with all their talk of transmigration of souls and their stupid dietary practices.”
“Don’t be obtuse, Decius,” Julia said. “Just listen.”
“I apologize. Please go on.” I knew better than to ignore that tone of voice.
“Aristobulus,” Callista continued, “is a scholar of the symbolic use of numbers and symbols. He is an advocate of a concept called the ‘unknown quantity.’ It is an extremely obscure and arcane field of study. Pythagoreans, with their mystical leanings, are about the only scholars who give it any serious attention. As far as I know, Aristobulus is the only one now working on the problem.”
She had lost me again, but I thought I understood her drift. “You think this has something to do with that—what did you call it?—that ‘symbol for nothing?’ ”
“Aristobulus uses the delta as his shorthand symbol for the unknown quantity. It is only a short step from that to a symbol for nothing at all.”
“This is making me dizzy,” I said, “but I trust your comprehensive knowledge of your field.”
I took the little scroll from her hand. It was finely made, enclosed in a leather tube with an ivory tag depending from one of the terminals. Written on the ivory in tiny, precise Greek letters, was the name of the author: Aristobulus of Croton.
My scalp prickled. Croton. Where had I heard that name spoken recently? Since this business had begun, my days had been so packed with events that I was beginning to lose track of who had told me what. To a Roman public man, educated to commit vast quantities of minutiae to memory, the sensation was disorienting.
“Decius?” Julia said. “You’re getting that look again.”
“What look?” Callista asked.
“The hit-on-the-head-with-the-sacrificial-hammer look,” my wife elucidated.
“I think he looks like a Dionysian reveler in a state of ektasis, the mind completely out of the body.”
“Isn’t that something like enthousiasmos?” my loving Julia inquired.
“No, that’s possession by the god. He’d be much more lively.”
“Instead of talking about me as if I weren’t here,” I said, “you could give me some help. I’m trying to remember where I heard Croton spoken of recently.”
“There was some question whether you were here,” Julia said. “And how can we help you remember? We weren’t there when it happened.”
“Let’s consider how the subject might have arisen,” Callista said. “For what is the city of Croton famed? It was the home of Pythagoras, naturally.”
“Let’s see”—Julia mused—“Croton? Athletes. Jewelers.”
“That’s it! The day before yesterday, Hermes and I found a seal ring in Fulvius’s desk. The lapidary I consulted said that the carving on the stone was in the style of the Greek cities of southern Italy. He was pretty certain that it was from Croton.”
“I love this sort of logic!” Callista said happily. “I know that applied logic is rather disreputable, but I find this exhilarating. But what is this about a ring?”
So I told her about this minor theft. What with murder and burglary and conspiracy and intrigues of one sort or another, it occurred to me that the felonies were beginning to pile up.
“If this conspiracy was hatched in Baiae as you think,” Callista said, “where originates the connection with Croton? The two towns are not close.”
“Baiae is about midway between Rome and Croton,” Julia put in. “It’s a substantial trip in both directions.”
“The conspirators,” I said, “wanted a code. As I’ve mentioned, certain senators follow the teachings of Pythagoras—not these men, of course, but one of them might have heard of Aristobulus in conversation. Or, who knows, one of them might have spent some time in Croton and studied with the man and knew of his theories. In any case, they probably hired him to devise this cipher for them. For a good fee, he would have been happy to go up to Baiae to confer with them.”