The Codebreaker — Craig Allen

Book 4 in the Devon McHenry adventures series. After 3 harrowing adventures, Devon McHenry, former SEAL and confirmed history buff, decides a proper vacation is in order. He heads to Germany, planning on slowly touring the Rhein, stopping at every castle and ruin along that historic river. When he stops at Köln he is given a mysterious packet of documents by a friend at his hotel, and suddenly his vacation become something much different. The package claims it will reveal the hiding place of a large number of Nazi/SS relics that current day neo-Nazis would love to have, but before he can begin the journey to find them he must decipher a message that is literally unreadable. In addition, he discovers that it's likely others are also on the chase. As he unearths a series of clues, each more cryptic than the last, he's also dealing with those chasing him, and he's finally forced to seek help from some of his old SEAL teammates. As they near the location of the actual cache more players emerge, and it become a mad dash to the finish line. If he can win the race, the prize promises to be great...but that's a really big if!