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The Celestial Guardian

A Vatican Secret Archive Thriller – Book 8

The Celestial Guardian is an exhilarating thriller that takes readers on a riveting journey into the heart of the Vatican’s secretive world and the enigmatic artifacts held within its vaults. The story revolves around Father Michael Dominic, Prefect of the Vatican’s Secret Archives, who discovers Leonardo da Vinci’s greatest creation—the Celestial Guardian, a machine designed to predict astronomical events. This discovery is initially viewed as a miraculous tool warning of a cataclysmic asteroid headed towards Earth. However, a deeper exploration of Da Vinci’s blueprint hints at a secondary, potentially dangerous function of the Guardian that extends beyond mere prediction—the extraordinary power to manipulate celestial events.

This revelation sparks a perilous pursuit for dominance over the Guardian. Its power to transform cosmic events into weapons of mass destruction lures various factions, including a Vatican cardinal blinded by ambition. As religious doctrines change and the Church comes under scrutiny, Father Michael grapples with his own emotional entanglements while racing against time to prevent global disaster. From the power corridors of the Vatican to the forefront of scientific exploration, the story delves into the complex interplay between science, faith, and human vulnerability, offering a thrilling narrative that questions where the line between miracle and science is drawn.

Set against a rich tapestry of Vatican mysteries and celestial secrets, the novel weaves historical intrigue with scientific discovery and human drama. The Celestial Guardian promises a journey filled with suspense, where ambition and the resilience of the human spirit collide amid cosmic threats, keeping readers gripped from start to finish.

Publication date: Kindle February 22, 2024
Paperback February 10, 2024

“I am always excited when Gary McAvoy reaches out with another of his novels, full of action and a number of teachable moments. While usually steeped in religious and Catholic history, McAvoy pushes into a more scientific domain, while tackling modern issues of astrophysics, Church doctrine, and international safety. There are still the core characters that series fans have come to enjoy, with some great development, both personal and story arc related. McAvoy does not disappoint in yet another thrilling novel within this stellar series.

While completing his daily tasks in the Vatican’s Secret Archives, Father Michael Dominic stumbles upon documentation related to one of Leonardo da Vinci’s most complex projects—the Celestial Guardian. Once deemed a highly advanced instrument that could predict celestial objects that might enter the Earth’s atmosphere and cause massive damage, further exploration by Father Dominic and those closest to him reveal another and more powerful aspect to the instrument. Keeping this under wraps is essential, but there are many with ears pressed against doors and who have spies in all corners of the Vatican.

As the Holy See is without a leader, a Conclave to elect a new pope is held, which leads to two diametrically opposed candidates vying for the position. When the white smoke exits the Sistine Chapel, Clement XV emerges and a new era on pontifical rule begins. This new direction could shape the future quite drastically, but also allow many to seek to influence the pontiff’s views. One such cardinal strikes as soon as possible, with knowledge of the Celestial Guardian to grease the wheels.

When news of the Celestial Guardian leaks outside the walls of the Vatican, as well as its power, many seek to have it for themselves. A plot to steal and utilize the Guardian takes place, putting one country ahead of the others as they try to manipulate the skies as well as defend the world from an ongoing asteroid that is hurtling towards Earth. As Father Dominic and his closest friends begin trying to decipher what’s happening, they learn that the sanctity of the Celestial Guardian has turned from being a piece of scientific knowledge into a weapon that could be used in the years to come. With his beloved journalist friend, Hana Sinclair, at his side, Father Dominic will have to fend off others and ensure the Vatican is not turned into a place for looting and creating new weapons of massive destruction. McAvoy does a masterful job with this piece to keep the reader wondering until the very end.

While I have always enjoyed Gary McAvoy’s writing about the Catholic Church in historical and modern times, I have also come to really enjoy his branching out into the impact of science on the Church and its policies. McAvoy does so here with da Vinci’s Celestial Guardian, illustrating the complexities of the device, its use, and the power struggle to possess its abilities. The narrative moves along at a fast pace and keeps the reader enthralled as events occur, posing a number of questions about ethical, political, and religious rights. The story’s momentum builds effectively and climaxes with a wonderful revelation that McAvoy surely hopes to ensure the reader ponders. With his great characters always evolving, the reader is permitted a generous glimpse into their intertwining, none greater than the Father Dominic/Hana Sinclair situation that has plagued series fans.

McAvoy has never struggled to create great plot points and developments to advance to story effectively. This is no exception, with a number of issues to tackle and resolve, McAvoy keeps the action high and the predictability low at times, juggling the concerns of many entities to develop a final solution for the main plot point, as well as hinting how one of the ongoing sub-plots might resolve itself. I have thoroughly enjoyed this series to date and am always eager to see what’s next, as things on the Holy See never seem to remain stagnant.

Kudos, Mr. McAvoy, for keeping things on edge until the final page turn.” — MATT PECHEY, Reedsy Discovery. “MUST READ” 5-Star Review


“Thanks to author Gary McAvoy for this intense, exciting addition to his brilliant series. This thrilling story combines religious history with ancient science based on the theories of Leonardo Da Vinci’s genius and modern scientific thought. It is based on astrophysics, mathematics, political and religious concerns with impending world destruction. Complex scientific knowledge and speculation take precedence over historical facts. The reader should not be deterred by some complicated science, as knowing only the purposes of the devices is all that is needed for the full enjoyment of this fast-paced, nerve-wrenching story. This is my favourite book in this brilliant series and works as a standalone, but new readers may want to read some previous books in the series as there are well-written returning characters. This time, scientific facts and speculation take precedence over historical facts and make for a terrific read.

Father Michael Dominic has discovered documents in the Vatican’s secret archives. They relate to Da Vinci’s long-lost Celestial Guardian. Its purpose was to predict celestial objects entering the Earth’s atmosphere and could constitute a threat to the world. He recruits a panel of scientists, including mathematicians, experts in astrophysics, and engineers, to assemble a modern instrument according to Da Vinci’s plans.

Once his experts assembled the Celestial Guardian under the leadership of Father Michael and his friend Hana, they were amazed at its accuracy extending into current times. It correctly predicted some historical cosmic events, but its relevance in modern times is more shocking. It shows an asteroid rapidly hurtling toward Earth. It is equivalent to the one that caused the extinction of dinosaurs and caused lethal climate change.

The existence of the Celestial Guardian has been leaked. Other forces plan to steal it and use it for their nefarious purposes. Three ruthless undercover agents from the CIA with expertise in burglary plan to steal it from the Vatican. This could lead to its use as a weapon with immense destructive powers. A new ambitious and duplicitous Cardinal plans to obtain it by using followers within the Vatican under his orders. He sees the Guardian as his opportunity to project false religious images into the sky, resulting in deceiving flocks of viewers into returning to the Church. This would enhance the Cardinal’s prestige and power.

So far, the public is unaware of the impending doom. The Celestial Guardian has now been stolen. Father Michael has tricks up his sleeves to stop all others who may have stolen the Guardian. Fortunately, Father Michael and Hana have discovered a long-hidden document in DaVinci’s words for a second scientific device that could cancel all intent by others to use the Guardian for destructive to deceptive purposes. Michael and Hana work feverishly to save the world from its upcoming doom while the terrifying asteroid continues its path toward Earth. They put the expert panel to work deciphering Da Vinci’s plans and constructing a second device that would make the Celestial Guardian useless for unknown groups that have obtained it through theft.

Highly recommended!” — CAROLYN WALSH, Canadian Reviewer