In the vast, enigmatic Sonoran Desert, a French scientist, Claude Lacombe, accompanied by his American interpreter and cartographer, David Laughlin, along with a team of researchers, stumbles upon a remarkable discovery: Flight 19, a squadron of United States Navy Grumman TBM Avenger torpedo bombers that mysteriously vanished over the Bermuda Triangle on December 5, 1945. The aircraft lie in impeccable condition, yet curiously devoid of any crew. Nearby, an elderly observer recounts a bizarre experience, claiming that "the sun came out at night, and sang to him." Meanwhile, air traffic controllers in Indianapolis witness two commercial flights narrowly avert a collision with an unidentified flying object (UFO).
In a tranquil home near Muncie, Indiana, three-year-old Barry Guiler awakens to find his toys animated as if possessed. Intrigued, he ventures outside, prompting his mother, Jillian (who is played by Teri Garr), to pursue him. Concurrently, widespread power outages begin plaguing the region, leading utility lineman Roy Neary (Richard Dreyfuss) to investigate the escalating disturbances. His exploration culminates in a jaw-dropping close encounter with a UFO, which grazes his face with its brilliant lights. As Roy and a convoy of police vehicles pursue the UFOs into the dark sky, the experience leaves him profoundly entranced.
The mystery deepens when researchers uncover the SS Cotopaxi, an intact ship found in the heart of the Gobi Desert, again completely empty.
As Roy's fascination with UFOs intensifies, his wife, Ronnie, grows increasingly concerned. His obsession culminates in a fixation on a particular mountain shape, leading him to create multiple models. Simultaneously, Jillian, sharing this relentless intrigue, begins sketching the same mountain. However, her life takes a turn for the worse when a UFO descends upon her home, assaulting her with invasive attempts from unseen entities. In the resulting chaos, Barry is abducted, heightening Jillian's desperation.
Amidst these unfolding events, Lacombe, Laughlin, and several United Nations specialists delve into the rising occurrences of UFO sightings and related phenomena. In Dharamsala, Northern India, witnesses report that the UFOs emit a unique sound: a distinct five-tone melody in a pentatonic scale. Scientists broadcast this musical phrase into space, only to receive an enigmatic series of numbers (104 44 30 40 36 10) in response. Laughlin, using his cartographic expertise, deciphers these coordinates leading to Devils Tower in Wyoming. This prompts a militarized response: the U.S. Army evacuates the area under the pretense of a train derailment caused by toxic gas while secretly preparing for the arrival of the UFOs and their passengers.
As Roy's unconventional behavior escalates, Ronnie decides to leave him, taking their three children with her. When a report airs about the purported train wreck, both Roy and Jillian recognize the mountain they have been fixating on. Driven by their vision, they set out to Devils Tower, undeterred by public safety warnings.
While most travelers are taken into custody by the military, Roy and Jillian successfully reach the site just as UFOs emerge in the evening sky. Government teams on site attempt to communicate with the craft through a combination of light and sound on an expansive electrical billboard. Eventually, a massive mothership arrives, releasing countless abductees from various eras—World War II pilots, sailors from the Cotopaxi, as well as humans and animals. Among those who return is Barry, who joyfully reunites with Jillian. Meanwhile, government personnel hurriedly prepare Roy for his selection to join the mothership's visitors.
As the extraterrestrials finally descend from the mothership, they choose Roy for interstellar travel. Upon his entry into the spacecraft, one alien momentarily engages with the gathered humans. Utilizing Curwen hand signs that correspond to the five-note melody, Lacombe facilitates a poignant communication. The extraterrestrial reciprocates the gestures, smiles, and then joins its counterparts as the ship ascends into the heavens.
