In Freud's essay "The Uncanny," he describes the eerie and strange feeling that he calls the uncanny, one closely associated with gothic literature and horror stories. The uncanny is unheimlich, or unhomelike. When we experience it, we are getting in touch with those parts of ourselves or of life that we usually repress. We try to repress what makes us uncomfortable or uneasy.
The symbol of the uncanny is the corpse: it is both completely human and completely inhuman at the same time, and it makes us uneasy. It shows us what we want to repress. In a similar vein, to avoid upsetting people, companies working on building robots try to make them fuzzy or animal-like because a "not quite human" creature is too creepy to want around.
Dolls or mechanical people of various sorts are uncanny for this reason, and Jerome exploits that creepiness in his story. Annette is bold enough to dance with Fritz, a mechanical dance partner. He looks and dances like a man, but with uncanny differences that make the other girls uneasy. For instance, the mechanical man is strange because he will
never kick you, or tread on your toes … or get out of step … or get giddy and lean on you.
He also has a
waxen face, with ... staring eyes and [a] fixed smile.
In other words, Fritz is not quite human. He suggests death, the ultimate strange and uncanny experience, because he makes
a harsh clicking noise in his throat, unpleasantly suggestive of a death-rattle.
All of this raises an uneasy sense of apprehension in the reader. This mechanical man brings to light the idea that everyone might not be what they seem, that beneath the "smile" of a dance partner might lurk an inhuman killer, exactly the kind of perception Freud argues we repress to cope with daily life and then express in safer form through horror literature.