In this sequel to Pulse, a genetic disease known as Brugada Syndrome kills its victims without warning, without symptom. When the president of the United States falls victim to a weaponized and contagious strain of the disease, the Chess Team - King, Queen, Rook, Knight, and Bishop - are assigned to protect Sara Fogg, a CDC detective, as she journeys to the source of the new strain: the Annamite Mountains in Vietnam.

Surrounded by Vietnam War-era landmines, harsh terrain, and more than one military force not happy about the return of American boots to the Ho Chi Minh trail, the fight for survival becomes a grueling battle in the humid jungle.

Pursued by VPLA Death Volunteers, Vietnam's Special Forces unit, the teams flight through a maze of archaic ruins reveals an ancient secret...a primal secret that may stop the disease from sweeping the globe, even as it threatens both the mission and their lives.