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.

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 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.

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.

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 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 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.

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.

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.

During a visit to the United States, Pope Pius XIV is caught within the crosshairs of a lethal assassin. After scores of people are killed during an event featuring the Pope's address, a conspiracy theory emerges that the killings were conducted by one of the CIA’s own. As the data trickles in, it becomes clear that the assassin is none other than Shari Cohen. 

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.

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.

When the Spear of Destiny is stolen by members of the Islamic State with its leader believing that the possessor of the Holy Lance has the ability to command powerful legions, they quickly find themselves in a position of "no escape" inside a towering skyscraper. Now that the power of the Holy Lance is in the hands of Ali Mustafa, he now finds himself with the opportunity to test its value and strength against those who dare oppose him. 

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.