In "The Keys to December" Jarry Dark is a genetically engineered human who looks anything but human. In his distant future of galactic corporations, his parents, wanting only the best for their son, had him genetically altered to be perfectly suited for the working environment of a planet newly prospected by General Mining, Incorporated. It is because of this that Jarry resembles a large, grey, tailless cat, whose optimum living conditions require at least -50°C, an atmosphere rich in methane, and 3.2 times Earth’s gravity. It is also because of this that he was essentially a ward of GMI. Under contract, the company agreed to assume all responsibilities in seeing that Jarry remained healthy, was provided with an excellent education, and that his family would suffer no economic hardships. In return for this, Jarry, and the other Catforms modified like him, would have to work for GMI for an unspecified portion of his adult life.

This was apparently common practice, and there were 28,566 Catforms scattered across the galaxy, all eminently suited to life on only one planet. Unfortunately, that planet’s sun went nova, and they were suddenly all faced with the prospect of spending their entire lives in the small "cells" that mimicked their proper environment. GMI was still obligated to provide for their needs in perpetuity, but what they really wanted was a planet which could provide them with a natural environment. Since there were none, Jarry and the others formed the December Club, and he used his economic talents to turn their pooled assets into enough capital to buy a planet that was a near-match and number of "Worldchange" units which would transform the global environment into just what they needed. This change would, of course, take a long time, so they also purchased cryogenic sleep chambers that would allow them to live to see the results.

The actual duration of the change was 3000 years, and various members would have to wake and take shifts every quarter-millennium to monitor the change and the equipment. After several hundred years, as it gets colder, the Catforms note that the small bipeds native to the planet have begun wearing furs and skins for warmth. As the change continues, Jarry himself discovers that the creatures learned to make more sophisticated garments, weapons, simple dwellings, and have learned to use fire. Upon meeting them personally around the halfway mark, he sees that they have developed a language, a rudimentary religion around the godlike Catforms, and even more startling physical characteristics: a pronounced forehead and an opposable digit!

There is now no doubt that these creatures, that were originally unintelligent and had been deemed unlikely to develop intelligence, have been forced by their rapidly changing environment to adapt or die, and that the Catforms have artificially accelerated their evolution. The problem is that many of the bipeds did die, and Jarry realizes that there is only so much their new-formed intelligence can do for them against such increasingly harsh conditions. There will come a time when they are physically incapable of further change, and the Catforms will be collectively guilty of genocide.

At this point, it is already possible for the Catforms to live, if uncomfortably, on the surface, and Jarry appeals to the leading members of the club that they should not allow the change to continue. They refuse. He tries every method available to him, but he loses the fight, and he chooses to live out the remainder of his natural life on the surface with the bipeds rather than see the future society, of which he wants no part.

Zelazny makes a very clear statement in this story about technology and moral action. He puts forth the idea that superior technology and power mean superior responsibility and demand superior morals. Not only are the Catforms responsible for the deaths of these less-advanced creatures, but they are also ultimately responsible for making them able to comprehend their own great suffering. Jarry, understanding this and unable to stop it, makes the only choice his conscience will allow and separates himself from those who don’t share his beliefs.