Hannah Bryson’s task as designer of highly technical submersible submarines used in mapping the underwater ancient city of Marinth becomes a dangerous mission. She works with her long-time friend, scientist Melis Nemid, who has made the mystery of Marinth and its sudden disappearance her lifetime study. National Geographic magazine has photographed their work, producing short documentaries about the undersea marvels they unearth. While trying to determine the reason for the once-thriving city’s demise, Hannah makes a shocking discovery that could have dire consequences for the modern-day world.

Iris Johansen and her son, Roy, weave together a plausible story about intrigue, international plotters, high finance between arms dealers, the CIA, two former Russian operatives from Cold War times, and Hannah Bryson herself. Hannah is fresh from the murder of her cohort and brother, Connor, who had been her best friend and close confidant, and has left behind a 12-year-old son, wife and daughter whom she cherishes. She is now back at sea in an attempt to wipe away her grief by helping Melis and her crew solve the Marinth mystery.

Hannah discovers a brilliant trellis, configured of small pieces of glass that forms a maze of language that only Melis can translate. Artfully driving and diving her submersible, she hooks the trellis behind it to drag it on a heavy sled up to the surface. But an eerie black formation that impedes the progress loudly crashes against the submarine, narrowly close to its destruction. Its force badly damages the vehicle, but Hannah is able to bring the treasure to the water’s surface. Her enemy deep near the sunken city is groups of dolphins, who butt the sub until it nearly shatters to pieces. On top safely, she and Melis can’t understand the unusual behavior of the usually mild-mannered mammals.

In the meantime, Hannah’s former love interest, Kirov, attacks and nearly kills a middle man for an international arms dealer, Gadaire, whose intent is to discover the scientific details of the research at Marinth. A possible link to the death of the ancient city comes from a lethal undersea growth from Marinth’s sea beds. The growth, which could have destroyed the ancient civilization, could now be a possible weapon in modern arms warfare between nations. Gadaire will sell the find to the highest bidder, making him possess the ability to unleash global terror. His lethal girlfriend, Anna Devareau, kills those who stand in his way, but she has plans to subvert him in order to gain control of his vast monetary empire.

Hannah discovers that her expedition is at risk but feels helpless to control the outcome without expert help. Through former KGB officer Eugenia, she contacts Kirov, and the plot becomes murky when strong but dark Kirov brings his findings to them. He’s in the sights of a CIA operative about his handiwork taking out Gadaire’s muscle man. Gadaire has contacted a biological scientist, a professor in Ireland, to experiment with the now-stolen trellis with its treasure from Marinth. Hannah, together with her team, Kirov, Eugenia, Baker from the CIA, and the entire research crew, must retrieve the stolen glass pieces to solve the maze. Melis can then possibly discover a tool to destroy the deadly specimens.

SHADOW ZONE is a quick read and too rapid-fire to put down. Its unique story is well researched but does not bog down with statistics. Hannah Bryson is still the feisty, stubborn heroine who recognizes that she cannot solve the mystery of Marinth without help from her complicated relationship with Kirov. Their interaction is not without trouble, but places two strong characters in unity when results bring help for the future. I highly recommend this latest Johansen venture as an entertaining read and look forward to more from this talented mother/son duo.