While on a visit to the United States, Pope Pius XIII is kidnapped by a terrorist cell calling itself the Soldiers of Islam. If the United States and its allies do not meet their demands, they will execute the pope. FBI Specialist Shari Cohen is called to duty to track down the terrorist cell responsible, and she soon learns that she is not alone.

Deep behind the Vatican walls, a secret order dispatches a clandestine group of elite commandos known as the Vatican Knights. Their mission: bring the pope back alive.

While traveling across the United States during the Papal Symposium, the papal plane, Shepherd One, is commandeered by a terrorist cell calling itself the Muslim Revolutionary Front. On board: a nuclear payload with half the yield that destroyed Hiroshima. Their demand to the US government: assassinate the five leading principals of Mossad.

Kimball Hayden is the commander of an elite commando group known as the Vatican Knights, a black-op force that works for the Church to protect its sovereignty, its interests, and the welfare of its citizenry. But Kimball is being stalked by someone from the past, a soldier who is stronger, faster, and far more brutal - an assassin so deadly not even the Vatican Knights can stop him.

Thirty years ago, the world was in the exploratory stages of creating a technology capable of artificial intelligence. Thirty years later, that technology has been perfected. In a lab somewhere in a remote mountain region in Iran, nanoparticles, or micro-bots, have been created to be self-sustaining and self-reproducing, each day evolving and learning from experience. They have been programmed to be the ultimate predator, devouring everything in their path and leaving nothing behind.

While vacationing in Paris, Shari Cohen's children are kidnapped by Jadran Božanović, a Croatian kingpin who runs a human-trafficking cartel and is as deadly as the knife he wields. Few dare to challenge him. And even fewer dare to defy him. With time running out and her resources running thin, Shari calls upon the aid of Kimball Hayden and his team Vatican Knights - an elite group of commandos dedicated to protect the sovereignty, interests, and citizenry of the Church - and are once again reunited.

In a Galveston, Texas lab, a lethal strain has been stolen by a terrorist faction. In New Mexico, the population of a small town is completely wiped out. In Las Vegas, a vicious underground clan called the Community surfaces at night to prey on the weak. In Paris, two old foes of Kimball Hayden reunite as a kill team to hunt him down. Now considered dead by the Vatican, Kimball Hayden is leading a secretive life on the streets of Las Vegas. But when a parish comes under the threat of a vicious mob, he finds himself thrown back into a world of violence.

When the pope is gunned down in an assassination attempt, Kimball Hayden and his team of Vatican Knights follow the conspiracy's trail to a cathedral deep inside the Brazilian jungle -- a place of taboo to locals who fear the Huecuvus, the Evil Spirits who protect those within the Ruins of Lost Souls.

Growing up with a sheltering mother and a belligerent father, Kimball Hayden's young life goes from one of innocence to the depths of chaos. When a vicious syndicate of murderers and extortionists begin to run the streets, Kimball soon becomes the focal point of their attention. His family is placed within the crosshairs, friends go missing or are found dead, all messages from the Gangster Prince. But when Kimball's world shatters and he grieves a great loss, the sleeping giant within him awakens.

In an abandoned church deep inside the Syrian Desert, Father Jenkins watches over a group of children who'd been orphaned by war and unrest. Having been marked for extraction by the Vatican Knights, a cabal of ruthless killers from the Islamic State cripples all attempts of safe passage and gives chase across a desert landscape that's completely ruled by scorpions and snakes.

After the march on the Vatican by the Islamic State, the radical group begins its push deeper into the European and American Fronts. But when the True Cross - the wooden remnants of the cross Jesus was crucified upon and the holiest of all relics - is stolen from the Church of the Holy Sepulchre by the Islamic State, it becomes clear that the relic is to be bartered to an arms dealer for weapons so devastating that Europe and the United States could be rocked to their very foundations.

Long before Kimball Hayden became a Vatican Knight, he once served as an elite assassin for the US government. After the ordered assassination on a United States senator by a cabal within the US command, Kimball is set up for failure and is believed dead by the Pentagon brass. But when a leading political principal involved with the senator's murder discovers that Hayden is alive, he's immediately seen as a threat to a certain few on Capitol Hill regarding the sanctioned hit on the senator, and those involved.

In Geneva, a highly valued product with the power to cause major destruction is stolen from the CERN. Eighty kilometers from the Austrian border, a young girl becomes the key that controls the will of the man with the power to create and destroy. In the mountainous regions of Switzerland, a hostile force from a pariah regime attempts to extract a scientist from a fast-moving train.

In Auschwitz-Birkenau in 1943, a place where ashes rain down on a daily basis to cover the ground with a mantle of gray, a rebel force of Jews band together in a fight for survival. Frederic Becher, an SS guard who falls in love with a Jewish girl, lays the groundwork for the creation of one of the most formidable forces in the world - the juggernaut that would eventually become the Vatican Knights.

When a cardinal is taken captive by an ISIS faction in Damascus, a team of Vatican Knights is dispatched to secure the cardinal's release. But having been ambushed and taken hostage themselves, only one man can bring them out. After Kimball Hayden walked away from the church months before, he is summarily called to duty by Vatican principals to rescue his team. But as Kimball works in the Dark to serve the Light, he discovers the truth behind the ambush and follows the trail of the betraying source directly to the Vatican.

In Washington, D.C., three priests have been murdered and mutilated with their corpses hanging upside-down in mock crucifixion. The only indicator as to the culprit is a 500-year-old order known as the Nocturnal Saints, an underground faction that had been borne from the Protestant Reformation and acts as judge, jury, and executioner against those deemed to be in contradiction of old-time traditions. So when Special Agent Shari Cohen of the FBI is called to track down this faceless enemy, she’s joined by the Vatican Knights, who have been dispatched by the pontiff to counteract the order.  

After a sacred tome written by the hand of Saint Peter is stolen from the Vatican’s Secret Archives, people around the world begin to die at the hands of a madman once the secrets of The Brimstone Diaries are unveiled. In Rome, a terrorist faction has quietly breached the ranks of the Vatican hierarchy. As the conspiracy within the ranks begin to materialize, the greatest threat to the Vatican State is about to commence with Vatican City caught dead-center within the crosshairs of total annihilation.

In Virginia, a Blacksite facility is assaulted with military sophistication to free a homegrown terrorist who once attempted to assassinate FBI Specialist Shari Cohen. Within days, two of America’s most iconic symbols of freedom are razed. In Rome, Kimball Hayden’s demons are at their worst, the man becoming a shell of his former self. But when he learns that Shari Cohen’s assassin is on the loose, he embarks on a trip of rediscovery that unites him with the woman he loves.

Before Kimball Hayden became a Vatican Knight, he was the commander of the Pieces of Eight, a kill squad that worked as part of a black-arm force of the CIA. He kills with impunity and acts with the cold fortitude of a machine. But when he begins to question the morality of his actions and the motives of his superiors, he is placed within the crosshairs by high-end principals who want to see him dead.

In central Syria, villages are razed as young men are conscripted to join the ISIS faction. In a Doctors Without Borders camp which is overrun by members of the Islamic State, people are abducted along with a priest Father Savino. He also happens to be the brother of the Vatican’s Secretariat of State. From the green zone in Iraq, Shari Cohen, now a CIA consultant and operator, learns that she must appropriate intel from the resurging ISIS force to stop them from striking international targets.

In Egypt, those within the Saint Catherine Monastery are brutally attacked and a secret that has been hidden for more than 3,500 years is stolen. In Zurich, an arms dealer makes an agreement with a band of elite terrorists for one-of-a-kind weapons of mass destruction, for a treasure that was presumed destroyed during the Exodus. When a conversation between two men is covertly videotaped by an operator of the CIA, Vatican Intelligence and the Mossad realize that the partial message received was filled with enigmas.