Dr. Eleanor "Ellie" Arroway, a dedicated scientist specializing in the search for extraterrestrial intelligence, makes a breakthrough when she detects a mysterious radio signal from the star system Vega. The signal, found to contain a repeating sequence of prime numbers, reveals itself to be a form of communication from an unknown alien civilization. With thorough analysis, Ellie and her team discover that embedded within the signal is a far more complex message: detailed instructions for constructing a machine of unknown purpose. This enigmatic blueprint sparks a mix of excitement, skepticism, and political intrigue as the project attracts global attention and significant debate over its implications. Ellie becomes a central figure in these discussions, vying for the opportunity to see the project through amidst opposition and power struggles.

As the machine's construction commences, Ellie faces not only technical and financial challenges but also personal ones, including her relationship with Palmer Joss, a spiritual philosopher who questions the broader meanings and consequences of the potential contact with an alien species. Despite the controversy and numerous obstacles, Ellie remains resolute in her quest to uncover the truth behind the signal. Her journey delves into deeper philosophical and existential questions about humanity's place in the universe, underscoring the intersecting realms of science, faith, and the human experience as the world awaits the completion and activation of the mysterious machine.