The pigpen cipher – also known as the masonic cipher, Napoleon cipher and tic-tac-toe cipher – is a geometric simple substitution code. It exchanges letters for symbols that form fragments of a grid. Usually, the pigpen cipher alphabet is derived from the following four grids:

It is the most popular secret writing alphabet in history and has been used to encrypt all manner of things, from gravestone inscriptions to treasure maps. Don your pirate hat and consult the key below to decode the chapter headings in this book!