The premise is a common one in science fiction. Somewhere, computers have acquired intelligence and have learned how to murder those who uncover their secrets. As Foo explains, it is "the old 'critical mass computer' idea, the computer that becomes aware, but with a new angle. Maybe it wouldn't be the size of the computer, but the number of computers." Apfel asks her, "Wouldn't it ... run our lives? . . . Would it take over?" Foo points out that such a nonhuman intelligence could be unfathomable: "Why should it care? How could we figure what its concerns would be?" This thin premise unifies a story that is primarily about two people who bear physical and psychological wounds that make them prisoners of the past.
Prisons of past, present, and future occupy most of the action of the story. It opens with Apfel being held captive by his telephone, which rings persistently until he not only answers it but follows the computerized instructions it dictates. Following instructions, he finds his reclusive next-door neighbor, Charles Kluge, who has part of his head blown off. Kluge is an alias for Patrick William Gavin, a pioneer in the development of computer technology. Kluge/Gavin had shut himself off from the world, never venturing out of his home. He was a prisoner of his own obsession with computers and the power they gave him. Also a recluse, Apfel is drawn out of his thirty years of cold gloom by Foo, the computer expert brought in to untangle Kluge/ Gavin's complicated web of intrusions into a multitude of computer records, including those of secretive government departments such as the National Security Agency. Press Enter focuses on Apfel and Foo drawing each other out of their psychological prisons.
Throughout the story, Kluge/Gavin's work menaces Apfel and Foo. "I've seen so much evil come from good intentions . . . And the chances of getting torn up like Kluge did are large." The knowledge that Kluge had acquired is dangerous, both for Apfel and Foo personally, and for the world at large that seems unable to cope with the manipulations of records made possible by Kluge/Gavin's computer network, Apfel notes that he is glad to see Foo destroying the information of Kluge/Gavin's huge store of floppy discs: "The old reactionary in me found it easier to believe There Are Things We Are Not Meant To Know." This attitude is disturbing, echoing as it does the Faustian curse of someone such as Kluge/Gavin destroying himself with a desire for too much knowledge.