In 1912 Wilfrid Voynich, an American rare-book dealer, made the find of a lifetime in the library of a Jesuit college near Rome: a manuscript some 230 pages long, written in an unusual script and richly illustrated with bizarre images of plants, heavenly spheres and bathing women. Voynich immediately recognized the importance of his new acquisition. Although it superficially resembled the handbook of a medieval alchemist or herbalist, the manuscript appeared to be written entirely in code. Features in the illustrations, such as hairstyles, suggested that the book was produced sometime between 1470 and 1500, and a 17th-century letter accompanying the manuscript stated that it had been purchased by Rudolph II, the Holy Roman Emperor, in 1586. During the 1600s, at least two scholars apparently tried to decipher the manuscript, and then it disappeared for nearly 250 years until Voynich unearthed it.

Voynich asked the leading cryptographers of his day to decode the odd script, which did not match that of any known language. But despite 90 years of effort by some of the world's best code breakers, no one has been able to decipher Voynichese, as the script has become known. The nature and origin of the manuscript remain a mystery. The failure of the code-breaking attempts has raised the suspicion that there may not be any cipher to crack. Voynichese may contain no message at all, and the manuscript may simply be an elaborate hoax...