The novel is about a female astronomer who misses her dead father. She is working for SETI (Search for Extraterrestrial Intelligence) to detect alien life by means of radio signals from distant stars and planets. She receives a message which is decoded as reading "1, 3, 5, 7, 11, 13, ...", which are the prime numbers. The SETI staff keep receiving messages from an alien civilization located on the star Vega. With the information sent from Vega, the scientists are able to build a machine that facilitates interestellar travel through wormholes.
The main character travels to Vega and meets someone who appears to be her father. She understands that he is not really her father but merely a creation that the aliens have formed using her memories. They speak a lot about science and the Earth and they say that they will help each other's societies in the future. She goes back to Earth but the government does not believe her story. She has no physical evidence because the cameras put on the machine only filmed static. She is told that she was knocked unconscious for a few minutes and never left Earth . However, her claim is reconsidred when it is discovered that the camera recorded forty-eight hours of static, rather than merely a few minutes..
Carl Sagan got the idea of using wormholes in the novel from a colleague called Kip Thorne, who was investigating the possibility of their existence and their use in interstellar travel.
The novel was adapted for the screen, with Jodie Foster starring as the astronomer.