Paul Christopher - The Templar Legion (Templar #5)

Retired Army Ranger Lt. Col. John Holliday is swept into an adventure as deadly as it is secretive when an archaeologist friend makes a bizarre find in Ethiopia. But when he follows a trail of clues through the chaotic and lawless horn of Africa, he finds himself hunted as he comes closer to a priceless treasure that can only be found by those who can solve a riddle from the past.