Set in a university genetics classroom, the story is a relatively straight discussion of genetics until Turtledove introduces specific details of the characters. In an interesting twist, one student asks his professor if it is possible that intelligent life could have evolved from something other than mollusks. The professor, whose name is revealed as Cthulhu, upbraids his student, Nyarlathotep, tapping one of his eight tentacles on the desk for emphasis. Evidently, in this alternate reality the chordates - which in our timeline include mammals as well as fish, amphibians, reptiles and birds - do not amount to much compared with the dominant mollusks.
The story is brief, but Turtledove makes the most of its length. The reader is lulled into a sense of security, as the professor explains in the importance of Hox genes. Then abruptly, Turtledove pulls the rug out from under the reader by revealing that all sentient life on Earth are mollusks. To add to the fun, Turtledove pays homage to H.P. Lovecraft by naming the characters after Cthulhu and Nyarlathotep, two of Lovecraft's monstrous creations.