Critic S. T. Joshi notes that the story demonstrates a "deftness of style, a subtlety in the build-up of a horrific climax, and a deep understanding of the psychological effects of horror.
[1] The author becomes involved in a mystery after a chance encounter with a missionary named Mortimer while traveling on an airplane.
The narrator realizes that the Chaucha are actually the Tcho-Tcho, which he had previously thought to be a fictional construct of Lovecraft.
The being is a black, fish-like humanoid demon called the Shugoran (roughly "Questing Man") with an appendage that resembles a horn attached to its face.
The story ends with his frightened next door neighbor having seen a black face at her window, something like a man wearing a gas mask or a snorkel.