The opening line of H.P. Lovecraft's story, The Whisperer in Darkness, tells us most of what we need to know not only about his approach but Jacques Tourneur's: "Bear in mind closely that I did not see any actual visual horror at the end." Like Jaws and Tod Browning's Dracula, what matters is the suggestion of horror coupled with the tension of suspense. Even as a kid, I had noticed that Lugosi didn't have fangs, but he still looked like he could--and would--bite.
It is the space just around the dark corner, not in front of one's nose, that makes one hesitate to move forward. Like anyone who is attracted to horror fiction and films, I have tossed around these ideas, as well as read others, such as Poe, Lovecraft, and King, on the art of composition of the unbearable. Sooner or later, they all get around to that moment at "the edge of night," as they stand above the dank hole, on the threshold of the old dark house, at the bottom of the silent stairs, and know they will go on, or that Something will come to them.
Both on their own and as a directing/producing team, Jacques Tourneur and Val Lewton understood the power of the whisper in the dark. In three tidy pictures--Cat People (1942), I Walked with a Zombie (1943) and The Leopard Man (1943)--they called to us in notes whose spell on later horror films has never been completely broken. Even Hitchcock's Psycho (1960) is mostly about suggestion: the shower scene is famous for being not nearly as explicit as the eye insists. But this is not quite the best example of the Lewton/Tourneur approach.
Better yet are those moments when we stand outside the Bates Motel looking up at the house, seeing silhouettes, hearing troubling arguments, waiting for Norman's mother to fly at someone once more; such is the effect of terror by implication. It is a kind of horror film noir, in which the sardonic grin of expressionism combines with the panic followed by weary submission of the great post-World War II crime films--one of which, by the way, Tourneur directed, Out of the Past (1947)--to produce a dreamworld in whose making we participate. In discussing the special effects of pre-CGI movies, Roger Ebert has often noted that contemporary effects simply show us the monster, but older films show us the filmmakers' imaginations at work. And I think this applies not only to Ray Harryhausen's stop-motion skeletons but also to Lewton/Tourneur's incessant fades to black just when we assumed our questions would be answered.