There has been another mass shooting in America, and thirteen people are dead. One of the victims is the daughter of Marco Barros, a powerful U.S. senator. The killer is still at large. Their identity and motive remain a mystery. Rookie ATF Agent Miranda Lopez's only lead is the murder weapon: an AR-15, a.k.a. the "black rifle."

Forced to work with Cal, a mysterious private sector mercenary hired by Senator Barros, Miranda's search for the rifle will take her across the country: from the crumbling city blocks of South Central, California to the frigid streets of South Side, Chicago to a sun-baked Arizona militia compound to the polished halls of power of Washington, D.C.

As they unravel a shocking grander conspiracy behind the shooting-- a dark secret that the powerful will do anything to keep hidden-- Miranda and Cal risk losing everything...