For the scene in which Marlowe is drugged, Edward Dmytryk showed Dick Powell falling through a sea of faces. He borrowed a trick from Saboteur (1942) by having the camera pull back from the actor to make it seem like he was falling. He also had the camera accelerate as it pulled back, to intensify the horror.
In order to make Mike Mazurki more threatening, Edward Dmytryk had the sets built with slanted ceilings to force the perspective. As Mazurki walked closer to the camera, he seemed almost to grow.
It was hard to get Mike Mazurki to tower over Dick Powell, because the former singer stood 6'2", with Mazurki--a former pro wrestler--only slightly taller at 6' 4-1/2". For many scenes, Powell had to stand in a trench.