The real mystery lurking in the chapel where Dan Brown set The Da Vinci Code.

Mitchell, a former cryptographer with the Royal Air Force, first stumbled upon the chapel nearly 40 years ago, when it was largely unknown and in disrepair. He would return to Rosslyn with increasing frequency over the years, always drawn to the cubes and their mysterious symbols. While there was no obvious order to the sequence of the cubes, Mitchell noticed that, as on a strand of DNA, little patterns would repeat. The same sequence of three symbols appears at the base of two of the arches, for instance, and one arch contains long stretches in which just one symbol is repeated.