‘NCIS’ Fans Aren’t Ready for Mark Harmon’s Announcement

Mark Harmon recently made an announcement that has been getting a lot of attention from NCIS fans—but it isn’t about returning to the series full-time.

The announcement is that Harmon has co-written a new nonfiction book with retired NCIS special agent Leon Carroll Jr. titled Ghosts of Sicily: The True Story of the Naval Intelligence Agents Who Courted the Mob to Fight Nazis in America and the Battlefields of Italy. The book was announced in early 2026 and was released on April 14, 2026.

According to the publisher, the book explores a true World War II story about how the U.S. Office of Naval Intelligence worked with organized crime figures to support Allied operations in Italy. Harmon said he has long been fascinated by WWII history and believes the newly uncovered details tell a compelling story.

Fans may have been expecting news about Gibbs returning to NCIS, but this announcement instead highlights Harmon’s continuing work as an author. It is also his second collaboration with Carroll following their 2023 bestseller, Ghosts of Honolulu.

While Harmon is no longer a regular cast member on NCIS, he remains involved with the franchise as the narrator and executive producer of NCIS: Origins, and he has continued to make occasional appearances connected to the franchise