Dr. Ellie Arroway, played by Jodie Foster, is a dedicated researcher for the SETI program stationed at the Arecibo Observatory in Puerto Rico. Inspired by her deceased father Theodore's passion for science and communication, Ellie uses her expertise to listen for radio signals from the cosmos, driven by the hope of discovering extraterrestrial life. Alongside her colleague, Kent Clarke, who is visually impaired yet shares her enthusiasm for the pursuit of the unknown, Ellie navigates the challenges of her mission with the assistance of research assistant Fisher.
In her personal life, Ellie finds herself in a relationship with Christian philosopher Palmer Joss, portrayed by Matthew McConaughey. During their time together, Ellie opens up about her atheism and the complexities of her fears and thoughts. Palmer, a part-priest writing about technology's impact on disadvantaged communities, brings a different perspective to Ellie's logical worldview. However, their relationship becomes strained when serious topics arise, forcing Ellie to distance herself.
Challenges emerge as David Drumlin, the president's science advisor, decides to withdraw funding from SETI, deeming it a pointless effort. Fortunately, Ellie secures support from the enigmatic billionaire S. R. Hadden, allowing her team to continue their groundbreaking work at the Very Large Array in New Mexico. Fast forward four years to 1996, Ellie finally detects a signal featuring a sequence of prime numbers from the Vega star system, about 26 light-years away. Just when hope arises, Drumlin and National Security Council advisor Michael Kitz attempt to seize control of her findings, causing turmoil within the project.
The signal not only reveals the prime numbers but also a historical video—Adolf Hitler's inaugural address from the 1936 Olympics—hinting at the first signal strong enough to reach another star and signal back to Earth. As the project garners intense global interest, Ellie finds a trove of over 63,000 pages of indecipherable data among the signal. Hadden clandestinely meets with Ellie to discuss the cutting-edge designs for a mysterious machine meant for a single occupant, aiming to decode its purpose.
Initially met with skepticism, the government's position shifts when Palmer reenters the conversation, advocating for the construction of the machine. Public pressure results in the creation of this transport at the Kennedy Space Center, where an international committee convenes to select a candidate for the historic journey. Despite Ellie being a prime candidate, her atheism leads Palmer to express doubts, ultimately favoring Drumlin for the mission to represent humanity better.
An unexpected tragedy strikes when a religious extremist targets the new machine, claiming several lives, including that of Drumlin. However, amid despair, a dying Hadden reveals the existence of a second machine in Japan, allowing Ellie to seize the chance to be humanity's representative. In an emotional reunion, Palmer expresses his previous reluctance to support her candidacy due to his feelings for her.
As Ellie prepares for the journey, she enters the machine, which propels her into a whirlwind of interstellar travel through a series of wormholes. She witnesses a radio-like structure at Vega and encounters an advanced civilization. In an astonishing twist, she finds herself on a beach reminiscent of her childhood drawings, where she meets a figure taking the form of her father. This alien explains that their appearance and setting were intentionally chosen to ease communication with Ellie, marking the beginning of humanity's fate among cosmic beings.
Upon returning, Ellie is met with skepticism as she recounts her incredible experience. The mission control team insists that her journey lasted only moments, contradicting her assertion that she was gone for roughly 18 hours. This discrepancy raises doubts, and a Congressional Committee forms to challenge her claims, speculating on the possibility of a ruse. In an ironic twist, Ellie appeals to the committee to embrace her truth based on faith, reflecting an almost spiritual conviction about her experience.
As the dust settles, Kitz and White House aide Rachel Constantine privately ponder the implications of Ellie's testimony, which recorded nearly an entire day's worth of static despite the chaos. Finally, Ellie and Palmer reunite, finding solace and renewed purpose as she continues her work at the Very Large Array.
