While FX ratchets up its promotion for the July 13 premiere of The Strain (there's a new behind-the-scenes video below), filmmaker Guillermo del Toro is already looking well beyond the first season.

Based on the bestselling novel trilogy by del Toro and Chuck Hogan, the horror series stars Corey Stall as Dr. Ephraim Goodweather, whose team from the Centers for Disease Control is called upon to investigate a mysterious viral outbreak with hallmarks of an ancient and evil strain of vampirism.

However, viewers shouldn't expect the adaptation to remain faithful to the source material, as del Toro reveals he's already spoken with showrunner Carlton Cuse about how he thinks the TV series should diverge from the books.

“With the TV show, if we see an actor we like, he lives longer,” del Toro, who co-wrote and directed the pilot, tells BuzzFeed. “We’ve taken liberties with that. We’re hitting the big guideposts of the book, but I never hold the book up and say, ‘Dammit, the book was different,’ because I know that you want to recognize the book but you don’t want exactly the same experience.”

To that end, he says there's enough material to explore in the three novels for five seasons.

“But then it ends,” del Toro says. “We will not go beyond the fifth season. I don’t want this to be a show that stays on until it’s not successful. I would like it to end the way the books are mapped. I don’t want to spoil, but we are going to do what we do at the end of the second book at the end of the second season — we will do that big finale. We know where we’re going and it’s exciting.”

The Strain premieres Sunday, July 13, at 10 p.m. ET/PT on FX.