In the code room of the Regalian palace, there is a wall carving showing the letters of the alphabet as "branches" off of each of the three main sounds. For example, if one heard a scratch (by itself, the letter A) followed by a tap; one would start at A and then move to the right on the chart to reach the letter D, and so forth. If one heard a scratch and then a click, on the other hand; one would start at A and move left to reach B. When viewed from a distance, the chart looks somewhat like a tree — hence the name. The code can also be represented more like a traditional Morse code chart, and is carved like this onto the floor of the code room. This form of the chart is reproduced below. The Code of Claw During the fifth book, the gnawers develop something called the "Code of Claw.” This code is not the same one referred to by the Tree of Transmission, though it is usually transmitted using the Underlanders' version of Morse Code. The gnawers' code is actually a cipher which uses "Gorger" (also an anagram of the word "Gregor"), with recurring letters removed to form "Gore" — each easily remembered by the rat armies — to make it more difficult to crack. In this code, each letter is "shifted" one over in the alphabet, except for the letters in the secret word, which stay the same. A becomes B, B becomes C, C becomes D, and so on. G, O, R, and E remain the same. This code is of great importance to continue the plot of Gregor and the Code of Claw because of its mention in the Prophecy of Gray and its usefulness to the human war effort. Film adaptation As of July 2019, Warner Bros. has purchased the film rights to the book series and have not yet announced when casting and filming will begin due to COVID-19. References Children's fantasy novels Fantasy books by series American children's novels Series of children's books Scholastic Corporation books