LOS ANGELES — Academy Award nominee Michael Keaton has pulled double-duty, returning to the directing chair and also starring in the new film “Knox Goes Away.”

"Knox" is the story of a hit man who is diagnosed with dementia, racing against the police to save his estranged son (James Marsden) and working to outrun the ticking clock of his own deteriorating mind.

Keaton’s character, John, suffers from a rare disorder, Creutzfeldt-Jakob Disease, which is similar to Alzheimer’s Disease, but with a much faster rate of progression. Keaton said it was the one thing, after reading the original screenplay by Gregory Poirier, that made him hesitate at the outset of the project.

“I immediately Googled it and asked around. I talked to Greg, the writer. I had heard about Creutzfeldt-Jakob Disease, but I didn’t really know anything about it," Keaton told Spectrum News. "It is fast acting. Once I felt like I really believed that, and an audience would really understand that, I thought, now I can start, how do we approach it,” he told Spectrum News.

“Knox Goes Away” also stars Academy Award winners Al Pacino, Ray McKinnon and Marcia Gay Harden.

Keaton says he was very fortunate in that he was able to share scenes with all of them. For Marsden, having Keaton as his father in the film was great but "weird."

“Weird in the age gap. I think he’s too young to be my dad. I’ll go have a beer with him, but look, I can go on about this man [Keaton]. He was such an inspiration to me when I got into this business. I wanted to be like him — that kind of career, I want those kind of choices and opportunities,” he said.

Marsden also tells Spectrum News that films like “Knox Goes Away” don’t get made anymore.

“I want to see these films. Maybe, this type of movie, to see it done as a film that is going to be on the big screen … that it is unabashedly for adults, I am so excited,” he said.

“Knox Goes Away,” Keaton says, is entertaining film that “makes you uncomfortable, but also, it is adults in the room. It is people telling an adult story. You don’t have to worry about the effects working all the time."

He tells Spectrum News that he has done his job if people find themselves falling into the story, wanting to know what's happening next and going home being satisfied.

"I hope people get lost there," Keaton said.

“Knox Goes Away” hits theaters this weekend.

Click the arrow above to watch the full interview with Keaton and Marsden.