"It's in some sort of code, Davus. Until I figure out the code, I can't read it any better than you can."

We had stepped from the garden into my study, and now sat across from each other at the little tripod table by the window, peering down at the thin pieces of parchment I had extracted from Numerius's shoe. There were five pieces in all, each covered with writing so tiny that I had to squint to make out the letters. At first glance, the text appeared to be pure nonsense, a collection of random letters strung together. I suspected the use of a cipher, with the added complication of mixing Greek and Latin characters.

I tried to explain to Davus how a cipher worked. Thanks to Diana, he had mastered the basic idea that letters could represent sounds and collections of letters could represent words, but his hold on the alphabet was tenuous. As I explained how letters could be shuffled arbitrarily about, then unshuffled, his face registered mounting bewilderment.

"But I thought the whole point of letters was that they didn't change, that they always stood for the same thing."

"Yes. Well…" I tried to think of a metaphor. "Imagine the letters all taking on disguises. Take your name: The D might masquerade as an M, the A as a T, and so on, and altogether you'd have five letters that didn't look like any sort of word at all. But figure a way to see through those disguises, and you can unmask the whole word." I smiled, thinking this was rather clever, but the look on Davus's face was now of confusion verging on panic.

"If only Meto were here," I muttered. The younger of my two adopted sons had turned out to have a genius for letters. His natural gifts had served him well in Caesar's ranks. He had become the general's literary adjutant. To hear Meto tell it, he had done much of the actual writing of Caesar's account of the Gallic Wars, which everyone in Rome had been reading for the last year. No one was more brilliant than Meto at cracking codes, anagrams, and ciphers.