Mark Harmon might have departed NCIS on camera, but he is still inspired by the agency every day.

So much in fact that he wrote a book about how the agency came to be!

Mark teamed up with Leon Carroll, Jr., who was a real NCIS agent, and together they wrote a nonfiction book about how the agency was formed.

Keep reading to find out more…

According to publisher Harper Select, the book, titled “Ghosts of Honolulu: A Japanese Spy, A Japanese American Spy Hunter, and the Untold Story of Pearl Harbor” will be released in November, and focuses on a case that was handled by the ONI, Office of Naval Intelligence.

Here’s the summary from the publisher: “Scrutinizing long-buried historical documents, co-authors Harmon and Carroll Jr. have brought forth a true-life NCIS operation that depicts the incredible high-stakes game of naval intelligence encompassing cultural complexities, life-threatening dangers, and unrelenting patriotism in this riveting historical narrative about the defining moment of a generation.”

“The book tells the story of Douglas Wada, the only Japanese American agent in naval intelligence, and Takeo Yoshikawa, a Japanese spy sent to Pearl Harbor to gather information on the US fleet. In his native Honolulu, Wada’s poses undercover as a newspaper reporter, translates wiretaps on the Japanese Consulate, and interrogates America’s first captured POW of World War II. In contrast, Yoshikawa works with the consulate as a junior diplomat and collects vital information, sending it straight to Admiral Yamamoto. Their dueling stories anchor Ghosts of Honolulu’s gripping depiction of the world-changing cat-and-mouse games played between Japanese and US military intelligence agents (and a mercenary Nazi) in Hawaii before the outbreak of the Second World War.”

Mark also spoke about how NCIS inspired him to write the book, saying, “I feel compelled to take part in opening up the history and real story of what became NCIS. When I first started this show, there was not much information to be found by research.”

He then explained that “NCIS agents are public servants at the highest level and many have come and gone through this life with no one knowing anything about who they are or what they do. And now that story gets told. All because of a TV show.”

Leon added that he hoped “this book will give readers a different look at NCIS as an agency and that we are much more than the homicide of the week. The name NCIS was chartered in 1992, 90 years after the establishment of ONI to emphasize the criminal mission of the agency.”

“Counterintelligence investigations and operations are an integral part of that criminal mission and play a very important role in our nation’s security. This book is intended to be the first in a series that will give an inside look into the inner workings of accomplishing that mission,” he said.

You can pre-order “Ghosts of Honolulu” now.

If you didn’t see, the cast was just announced for the latest NCIS spinoff, NCIS: Sydney.