Did the Masons encode messages in walls--and even in the street plan of Washington, D.C.? Does the Hebrew Bible conceal hidden mysteries? Ingenious methods for encoding secrets have taken many amazing turns through the ages, from the military signals the Romans flashed from hilltop to hilltop, to the computer codes that guard your cash at the ATM. Pierre Berloquin, one of France's leading puzzle book authors, takes you on a tour of them all in a book full of astonishing historical insights. With more than 150 brain-teasing problems for readers to solve for themselves, this is a journey beyond the gee-whiz and deep into the how-to of codes, ciphers, and other secret communication systems.