The Devil's Tail

A Revealing Eraser was a magical stationery item that could make invisible writing visible. Aside from being red, it was no different from an ordinary Muggle eraser.

That eraser was what Pomona had used to help Severus cheat. She had written the key on the menu from the table where they had sat, and he could see the key, "Coconut," by rubbing it with the invisible eraser.

Caesar ciphers were a common way for "heretics" to pass messages during the Renaissance. Even if something happened to the messenger along the way, they did not have to worry about the "enemy" discovering the secret in the letter.

Gianluca had been surprised that Monica knew Caesar ciphers. Somehow, they ended up talking about the Zodiac Killer. His symbol was a cross inside a circle. Gianluca thought it was a sniper scope, while Monica believed it was the symbol of some Christian sect.

The Celtic Cross looked rather like the symbol drawn by the Zodiac Killer: a cross inside a circle. In Christian culture, the combination of a circle and cross represented heaven and earth, as well as eternal life.

In Germany, because the Celtic Cross had been adopted by a banned neo-Nazi party, the German government prohibited its public display.

The problem was that the Greek cross had equal arms, while the Celtic Cross did not. Crosses were universal symbols that had existed since ancient times, representing the Babylonian sun god. They were usually combined with an enclosing circle to form a sun wheel. The books they had looked through that day contained those symbols.

If there was one serial killer Pomona least wanted to encounter, it was the Zodiac Killer. He was full of rage. He claimed to have killed thirty-seven people, though only eight had been confirmed. His victims were