The shark didn’t work: I repeated these words to myself often when it was time to write one of the scarier scenes in my new supernatural thriller, The Heavens Rise.

If you’re anything like me, there was your childhood before you saw the opening sequence of Stephen Spielberg’s Jaws— and then there was your childhood afterward. When I look back on both periods, they feel like different lives altogether.

In the former, the ocean was a peaceful, tranquil place. Since the latter period, the ocean is a demon’s lair, filled with bloodthirsty nightmares.

But if you’ve ever read anything about this classic of terror, you probably know that Spielberg planned to make a very different kind of film. In storyboard artwork of that opening shark-attack scene, the giant great white is depicted rearing up out of the water, the hapless skinny-dipper clamped in his jaws. The scene didn’t get shot that way for one very simple reason: The shark didn’t work.

In fact, the mechanical sharks built for the film proved so temperamental once they were put to sea that Spielberg was forced to re-conceive his entire approach to the movie. And what started as a Japanese horror film at sea, with scenes of a giant man-eater bursting from the waves every fifteen minutes or so, became something else altogether: a masterpiece of modern terror. Because, as my best friend and co-host of The Dinner Party Show, Eric Shaw Quinn, reminds me constantly: What is scarier is what you can’t see. Far scarier than any mechanical shark or man in a rubber monster suit is the monster you have to imagine for yourself.

Don’t get me wrong. I try for plenty of of shocks and chills in The Heavens Rise. And every reader has a different line-in-the-sand when it comes to blood and guts (and sex, for that matter), so it’s impossible to assert some universal standard for “what’s-just-too-much.” But much of the book centers around a character named Marshall Ferriot, a complete psychopath hell-bent on revenge against the girl who rejected him sexually in high school. And oh, by the way, Marshall has the power to control your mind. As in, total, unrestricted control. And there’s no helmet or shield or chemical that can stop him.

While the potential for gore and sadism with such a storyline is infinite, I tried to bend in the direction of genuine fear, as opposed to actual nausea. (Indeed, I’ve found so much of recent horror films to be so brutal and sadistic, I questioned whether I had any business at all writing in a genre that could reasonably be described as horror.) Close to the end of the revision process, I received a note from my editor suggesting I had come close to my goal. “What’s terrifying in this scene is not what Marshall does do, but what he could do at any given moment.”

Bingo.

As with Spielberg’s shark, whose suggested presence below the water-line is much scarier than his giant rubber mouth lunging at the camera, Marshall Ferriot is a character who vibrates with terrible potential in every scene he enters.

And in my opinion, that’s a lot scarier.