Best-selling Camden author Tess Gerritsen and her son have teamed up to make an indie horror film titled “Island Zero” around Camden and Rockport this month.

The screenplay was written by Gerritsen and the movie is directed by her son, Josh Gerritsen, a professional photographer in New York and a documentary filmmaker. The producer is Mariah Klapatch, a Camden native and longtime friend of the Gerritsens who has made commercials and videos in Los Angeles for a decade.

The best known of the film’s cast is Laila Robins, a veteran theater and TV actress who played the ambassador to Pakistan on the Showtime cable series “Homeland.”

About 35 people make up the cast and core crew, with many others helping part time. About 80 percent of those working on the film are from Maine, Klapatch said.

Gerritsen said Monday the film sprang from a casual mention to her son that she’d love to write a horror film like “the old classics” she loved as a child, when horror movies were more than just “teen slasher flicks.” Her favorite is “Invasion of the Body Snatchers” from 1956.

The story of “Island Zero” focuses on the people of a remote island off Maine who find themselves without power or any way to communicate with the mainland after the ferry stops coming. Then people start dying.

“With this story about isolation, the sea and hardy islanders, it was obvious that Maine was the place to film,” Gerritsen said.

Gerritsen, a former physician, has written suspense and medical thrillers among her books, which have sold 30 million copies. Her series of novels teaming homicide detective Jane Rizzoli with medical examiner Maura Isles is the basis of the TNT TV series “Rizzoli & Isles.”

Filming for “Island Zero” began last week in Camden and Rockport and will continue in midcoast towns and on Islesboro until March 26. Klapatch said the film is scheduled to be finished by September and then submitted for entry into film festivals. The filmmakers hope festival showings will lead to a distribution deal that lands the film in theaters at some point.

During the first week of filming, the cast and crew have been welcomed by local residents and businesses, Klapatch said. Two of Klapatch’s neighbors offered their homes for interior shots. Other locations where scenes have been or will be shot include the Swan House Bed and Breakfast in Camden, Victorian By The Sea in Lincolnville, the ferry terminal on Islesboro, and areas around Camden and Rockport harbors.

“People are just so eager and excited to help; it’s very different from shooting projects around major production hubs like Los Angeles and New York,” Klapatch said, adding she hoped the film might lead to more film projects coming to the state. The independent film has a budget of up to about $400,000 and is being financed directly by the Gerritsens, Klapatch said.

Gerritsen’s latest novel, “Playing with Fire,” is a suspense novel that begins when a violinist finds an obscure piece of music in an antique shop and finds it has a horrible effect on her young daughter. Gerritsen wrote the music as well.