The historian carefully leafs through pages of a 400-year-old, leather-bound book until she finds the shaky signature. It’s a faint scrawl that has consumed Tamara Estupinan for more than 30 years, led her to find forgotten Inca ruins and sparked an academic firestorm.

The signature, she says, is the key to unlocking two of archaeology’s greatest mysteries: What happened to the body of Atahualpa, the last king of the Incas? And what became of his fabled treasure?

Estupinan thinks she has the answer to both questions. And while she hasn’t found gold, she may have uncovered something considered even more precious.