"The Key" is a short story (described as a novelet), written by Isaac Asimov and published in the October 1966 issue of The Magazine of Fantasy & Science Fiction.
The particular issue of this magazine was dedicated to Isaac Asimov. Fantasy & Science Fiction has a tradition of occasionally basing a magazine around a certain author: usually featuring a story by them and then having some biography or autobiography included. When this issue was published, the tradition was just starting, and even today only a dozen or so writers have had an issue dedicated to them. Having this done is a type of canonization. By 1966, Isaac Asimov had already been canonized, having been published for twenty five years.
All of this is important to understand the story of "The Key", which is about two astronauts exploring the moon, in the near future, who stumble across a device left by some ancient, powerful civilization. The device is an empathetic transmitter, and one of the astronauts sees this powerful tool as a possible weapon. It turns out one of the astronauts is an "Ultra", a movement dedicated to eugenics and primitivism. His companion astronaut, the hero of the story, is not, and decides that this powerful device must be hidden. He runs away and dies somewhere on the moon, after hiding the device and leaving a cryptic message as to its whereabouts. This opens the second part of the story, the attempt of the police to find the hidden device. The story cleverly concludes by explaining what the cryptic message is trying to say.
The story is good, readable and interesting. But I do think it is a sign of how science fiction has altered. Slightly earlier in the year, the Magazine of Fantasy & Science Fiction published "We Can Remember it For You Wholesale", a story that would be a prelude to Phillip K Dick's entire ouvre of mindscrew stories. What is interesting is that after reading these two stories, I would say that Isaac Asimov's story is better written, and reaches its conclusion better. And yet this story of Asimov's is not well remembered. Its major messages seem to be that fascism is bad and that Isaac Asimov is a clever writer---both of which we already knew. On the other hand, Dick's story, which is barely more than a sketch, is widely canonized in the history of Science Fiction.
None of this is to slight the story, which is entertaining, and well constructed. It just shows that in Science Fiction, as in other fields, what is considered important at the time may not always be so.