The narrative unfolds with the sudden reception of musical signals from space, first detected by a satellite-tracking station in the South Pacific. The signals, described as flutelike and melodic, are confirmed to be of artificial origin, leading to widespread excitement and fear among scientists and the public. As the signals are picked up by various global stations, it becomes clear that they are a communication from an unknown source, prompting a sense of urgency and curiosity about humanity's place in the universe. Joe Burke, a development engineer, is drawn into the mystery when he realizes that the signals resonate with a recurring dream he has had since childhood, involving a world with two moons and strange trees. This dream has always left him feeling incomplete and unable to pursue a romantic relationship with his secretary, Sandy Lund. The arrival of the signals reignites his obsession with the dream and the possibility of extraterrestrial life. As the story progresses, Burke and his colleagues, including Sandy and a few engineers, embark on a mission to investigate the source of the signals, which is traced to a small asteroid known as M-387. They discover that the asteroid is hollow and equipped with advanced technology, including weapons and a transmitter that has been sending out distress signals for millennia. The crew learns that the fortress-like asteroid was once inhabited by a civilization that has since vanished, leaving behind a call for help. Burke's connection to the signals deepens as he realizes that the black cubes found within the asteroid serve as instructional devices, allowing him to access the memories and experiences of the fortress's former inhabitants. This revelation leads to a sense of urgency as they understand that an impending threat from an unknown enemy is approaching, prompting them to prepare for potential conflict. The narrative explores themes of isolation, the search for identity, and the implications of encountering advanced extraterrestrial technology. As Burke grapples with his feelings for Sandy and the weight of his dreams, the crew must navigate the complexities of their situation, balancing their personal desires with the looming threat of an alien force. Ultimately, the story culminates in a confrontation with the unknown, as Burke and his team must decide how to respond to the signals and the potential return of the fortress's original inhabitants or their enemies. The tension between human emotions and the vastness of space serves as a backdrop for the exploration of what it means to be human in the face of the unknown.
By Murray Leinster · First published 1950 · Genre: Science Fiction, Space Opera, Adventure · 10 chapters