Contact recap

Radio astronomer Ellie Arroway leads a search for extraterrestrial intelligence and detects a signal from Vega built around prime numbers. Beneath an initial broadcast image, researchers uncover an immense technical Message: instructions for a Machine whose purpose is unknown. Nations cooperate and compete to build it. After the first American Machine is destroyed by a bomber, a secret second installation is completed, and Ellie joins four international travelers. The device carries them through a network of cosmic stations to a meeting arranged by advanced beings, one of whom appears to Ellie as her dead father. They are told that many civilizations share this network and that the universe may contain signs of deliberate design. Back on Earth, no measurable time has passed, leaving the travelers unable to prove their account. Officials publicly dismiss it, although hidden recording data supports the elapsed time they report. After learning that John Staughton was her biological father, Ellie finds a striking geometric pattern deep in the digits of pi and continues searching.

Eleanor Arroway grows up fascinated by radios, numbers, and the problem of how anyone can know what is true. Her father Ted encourages that curiosity, and his sudden death leaves her with a lasting grief and little patience for consoling claims that cannot be tested. She becomes a radio astronomer and commits herself to SETI, despite resistance from senior scientist David Drumlin and others who consider the search wasteful. At the Argus telescope array in New Mexico, Ellie and her colleagues detect an intensely powerful signal from the direction of Vega. Its pulses follow the prime numbers, ruling out an ordinary natural source and strongly indicating intelligence. Confirmation at observatories elsewhere turns a private scientific triumph into a discovery with worldwide consequences.

The Vega signal continues, and researchers discover that it contains several nested layers. One layer carries a retransmission of an early television broadcast from Earth, showing that the senders have received human signals and returned one as a marker. Another, much larger layer resists interpretation until the industrialist S. R. Hadden points the investigators toward a hidden organizing scheme. The recovered pages prove to be technical instructions for a vast and costly Machine. They do not explain clearly what it will do or establish the senders' intentions. Governments, scientists, and the public divide over whether construction would be humanity's greatest opportunity or a trap. Because no nation can master every part alone, the Message begins forcing cooperation even as rival states compete for control.

An international consortium coordinates the decoding and proposed construction of the Machine while political and religious arguments spread around the discovery. Ellie meets Palmer Joss, a respected religious thinker who presses her on the limits of proof and questions what kind of trust the project requires. Their disagreement becomes personally important without erasing their opposing standards of evidence. At government meetings, science adviser Ken der Heer tries to mediate between researchers and leaders, while security official Michael Kitz emphasizes strategic danger and the possibility of deception. The complete plans describe a device with five places for human occupants. With the Machine now physically conceivable, the central disputes shift from whether the Message is real to who should build, control, and enter it.

The Machine is assembled from the Message's instructions, and candidates from several nations are evaluated for its five seats. The project brings together Ellie, Soviet astronomer Vaygay Lunacharsky, physicist Abonnema Eda, physician Devi Sukhavati, and scholar Xi Qiaomu, though American institutional politics initially favor David Drumlin over Ellie. Palmer Joss cannot endorse Ellie's certainty about the senders' benevolence, complicating both the selection debate and their relationship. During a test at the American site, a religious extremist's bomb destroys the installation and kills Drumlin along with many others. Hadden then reveals that a second Machine has secretly been built in Japan. Ellie takes the vacant American place, and the five travelers enter the completed device as it prepares to activate.

The Machine activates and carries its five passengers through a sequence of apparent wormholes and enormous transit stations linking distant parts of the galaxy. They arrive at a constructed landscape where each encounters a representative who assumes a personally reassuring human form. Ellie's visitor appears as her dead father. He explains that the transport network serves many civilizations and that humanity is only a recent participant in a much larger community. The beings did not create the network and are themselves trying to understand still deeper signs of purpose in the cosmos. The travelers are given no simple public proof to take home. After what seems to them like many hours, their return journey begins, while observers on Earth see the Machine fall back without any visible interval of absence.

The five travelers return together with consistent memories of their journey, but Earth instruments show no elapsed time and their recordings initially appear to be only static. An inquiry led by skeptical officials treats their story as a likely fraud connected to Hadden, who dies after leaving Earth and cannot answer the accusation. Ellie refuses to recant an experience she cannot demonstrate. Palmer Joss accepts her sincerity, reversing their earlier positions by asking that her unsupported testimony be trusted. Kitz and der Heer privately discover that the supposedly blank instruments contain many hours of recorded noise, matching the duration claimed by the travelers, but keep the finding secret. A final letter from Ellie's mother reveals that John Staughton was Ellie's biological father, forcing her to reconsider the family history she had defended. Pursuing the visitors' hint that order may be built into mathematics, Ellie searches the digits of pi in base eleven and finds a vast sequence that forms a circle. The pattern offers no public resolution, but it gives her evidence of an intelligence or structure deeper than the Vega Message, and she continues the search.

The five travelers return at the same instant they left, although each remembers many hours passing and all describe the same network of cosmic transit stations. Their instruments appear to contain only noise, so an official inquiry treats the journey as an elaborate deception associated with Hadden. Palmer believes Ellie's testimony because she now asks others to accept an experience she cannot prove. Kitz and der Heer privately learn that the recording devices contain many hours of blank data despite the Machine's apparently instantaneous activation, but they suppress that anomaly. Ellie also receives her late mother's letter and learns that John Staughton, not Ted Arroway, was her biological father. Continuing her research, she tests a suggestion that a maker might have left a signature inside mathematics itself. Far into the base-eleven expansion of pi, a long sequence forms a circular pattern, giving her private evidence of order embedded in the universe. The public case remains unresolved, while Ellie resumes her search with a changed understanding of evidence, faith, and human importance.