Kate and Ruth trek up Prospect St. — "if Kate G. looks at the…"
if Kate G. looks at the images of passersby in the darkened shop windows they become (pedestrians and undead stem-artists) just heads that seem to float across each window unconnected to anything. As in disconnected floating heads.
Context
Kate's perceptual field inside It: the street de-bounded into heads floating unconnected across dark glass. It's also the device by which the plot springs its trap — one of the heads she does not see is Poor Tony Krause's, several steps behind and matching their course.