This is the first book in a series. It opens and ends in the same way, with FBI Agent Atlee Pine questioning the man she believes killed her twin sister when they were six years old. 

Sandwiched between these prison visits is a story of national security that has absolutely nothing to do with Atlee and her sister. Bad actors pull strings from the higher echelons of the United States government, and it soon becomes Agent Pine's duty to stand against them in a race to solve a mystery that starts with a dead mule in the depths of the Grand Canyon. 

This was a quick, interesting read.