While on a horror movie set with his Uncle Dervish, Grubbs Grady realizes that his battle with the evil demon master Lord Loss may be about to resume.

Greg Heffley's mom wants him to take a break from video games while Halloween approaches and he comes up with an idea to make a movie.

"Ryuji Goda, Art Squad president and sterling example of self-confidence, has become anxiety-ridden Ranmaru's greatest role model. Surely under the guidance of such a genius, Ranmaru will come into his own? But now a film camp at a remote mansion is putting Goda's assurance to the test. Is Ranmaru up to the challenge of saving his mentor from his greatest fear--a child?"--Back cover.

Everyone is excited when the McMurray dairy farm is chosen to be the setting of a movie, especially best friends Mary and Jody who see it as an opportunity to show off their ponies Lady and Star.