The novel begins in the year 2019, when the SETI program, at the Arecibo Observatory, picks up radio broadcasts of music from the vicinity of Alpha Centauri. The first expedition to Rakhat, the world that is sending the music, is organized by the Jesuit order.
Only one of the crew, Father Emilio Sandoz, a priest, survives to return to Earth, and he is damaged physically and psychologically. The story is told in framed flashback, with chapters alternating between the story of the expedition and the story of Sandoz' interrogation by the Jesuit order's inquest, set up in 2059 to find the truth. Sandoz' return has sparked great controversy – not just because the Jesuits sent the mission independent of United Nations oversight, but also because the mission ended disastrously. Contact with the UN mission, which sent Sandoz back to Earth alone in the Jesuit ship, has since been lost.
From the beginning, Sandoz, a talented Taino linguist born in a Puerto Rican slum, had believed the mission to Rakhat was divinely inspired. Several of his close friends and co-workers, people with a variety of unique skills and talents, had seemingly coincidental connections to Arecibo and one of them, a gifted young technician, was the first to hear the transmissions. In Sandoz's mind, only God's will could bring this group of people with the perfect combination of knowledge and experience together at the moment when the alien signal was detected. These were the people who, with three other Jesuit priests, were chosen by the Society of Jesus to travel to the planet, using an interstellar vessel made out of a small asteroid.
Sandoz tells about how the asteroid flew to the planet Rakhat, and how the crew tried to acclimatize themselves to the new world, experimenting with eating local flora and fauna, then making contact with a rural village – a small-scale tribe of vegetarian gatherers, the Runa, clearly not the singers of the radio broadcasts. Still, welcomed as