In 1939, U.S. Air Corps test pilot Captain Daniel McCormick learns that his best friend, military scientist Harry Finley, has made a major breakthrough in cryonic technology after successfully reviving a chicken that had been frozen. Daniel shares the news with his sweetheart, Helen, but reminds her that the development is top secret. At Harry’s engagement party, Daniel is inspired to propose to Helen before she departs on an important work assignment. He invites her to a diner for an impromptu date, but cannot muster the courage to pop the question. As Helen leaves the parking lot, she is hit by a truck and falls into a coma with little hope of recovery. Daniel spends the next six months in reclusive depression, unable to comprehend his future without her. Meanwhile, Harry intends to move ahead with his experiment by freezing a human test subject for one year, and Daniel volunteers, hoping to be spared the pain of watching Helen die. Fifty-three years later, ten-year-old Nat Cooper accompanies his friend, Felix, to the dentist. On the way home, Felix’s older brother, Steven, stops at a military warehouse to drop off some paperwork before the facility’s impending demolition. Despite Steven’s strict instructions to stay in the car, the boys run through the storeroom and discover the capsule containing Daniel’s body in a state of suspended animation. Pretending it is some kind of submarine, they twist several knobs and levers, causing it to open. Suddenly, Daniel’s arm reflexively jerks forward and grabs Nat’s jacket, frightening the boys away. Several hours later, Daniel, fully revived, stumbles outside and takes some clothing from a clothesline. Realizing he has awakened in 1992, he reports his story to Lieutenant Colonel Wilcox, who assumes he is insane. With nowhere else to turn, Daniel reads the name and address label sewn into Nat Cooper’s jacket and tracks down the Coopers’ home. Nat helps Daniel use the phonebook to call possible relatives of Harry Finley and go to the local library to read microfilmed newspapers clippings. As Daniel searches the headlines, Nat becomes distracted by the arrival of his crush, Alice, who seems largely uninterested in his advances. A librarian informs Daniel that records on Harry Finley could take more than six weeks to produce, but she finds the pilot charming and agrees to expedite the process. Keeping Daniel’s presence a secret from his single mother, Claire, Nat sets up a bed in the backyard tree house. Before long, however, Daniel intervenes when Claire’s alcoholic ex-boyfriend barges into the house and beats her. Daniel fights him off, and Claire, a nurse, gratefully tends to his wounds and agrees to let him sleep on the couch. The next morning, Daniel rushes to meet a man named Harry Finley, but is disappointed to learn it is not his friend. Afterward, he stops by the military base, where the annual “Wings of Freedom” air show is taking place, and inspects the now-vintage airplanes he once tested. He runs into Claire, who is there with Nat and Felix. Claire sympathizes with Daniel’s loneliness and allows him to stay a few more days, much to the chagrin of her latest boyfriend, John. The next day, Daniel comes across the diner where he tried to propose to Helen and sits in the booth they once shared. Later, as Daniel helps repair a hole in the Coopers’ roof, Nat asks for advice on wooing Alice, the girl from the library. Daniel responds that Nat is too young to be preoccupied with romance, and suggests he forget about her. Suddenly, he feels a sharp pain in his chest, loses his balance, and nearly falls off the roof. That night, Claire plays a Billie Holiday song on her CD player, triggering painful memories of Daniel’s relationship with Helen. As he cries, Claire embraces him, and they share a gentle kiss. Once Claire leaves for her shift, Daniel bursts into Nat’s room to amend his earlier advice, and encourages the boy to be honest about his feelings before he loses his chance. Inspired, Nat climbs a tree outside Alice’s bedroom window and serenades her with “You Are My Sunshine,” which deeply embarrasses her. The next day, Daniel prepares to leave, but first gives Nat a mock flying lesson in the tree house. Suddenly, Daniel doubles over in pain and is rushed to the hospital where Claire and John work. John determines that Daniel has a blood mutation causing him to rapidly age, and Daniel admits he is actually eighty-five years old. Meanwhile, Lt. Col. Wilcox finds Daniel’s cryonic chamber outside the warehouse and contacts a government scientist named Dr. Cameron. With the Federal Bureau of Investigation (FBI) stationed outside the hospital, Claire smuggles Daniel into her car and takes him to the home of another person who responded to his telephone search. They meet Harry Finley’s adult daughter, Susan, who recognizes Daniel from her father’s photographs. A warehouse fire broke out shortly after Daniel was frozen, and Harry died trying to save his chamber from being damaged. Official military reports stated that Daniel also died in the blaze, while the cryonic capsule was mislabeled in the warehouse inventory and effectively forgotten once World War II broke out. Susan uncovers her father’s old scientific journals, which contain notes about the irreversible side effects, including Daniel’s symptoms of rapid aging. When Daniel sees a picture of Helen, Susan reveals that she fully recovered from her accident and now lives alone on the coast as a widow. With the FBI in pursuit, Claire drives toward Helen’s house, but Daniel feels his body deteriorating and insists on a faster mode of transportation. Helen takes him to the air field, where he steals a B-25 bomber, unaware that Nat has sneaked onboard. Once he takes off, Claire avoids arrest by giving Dr. Cameron the notebooks belonging to Harry, in which the scientist claimed to advance the possibilities for long-term space travel. As Daniel flies over Helen’s seaside home, Nat crawls into the cockpit and helps land the plane, since the pilot’s health is quickly fading. Now resembling his true age, the weak and white-haired Daniel approaches Helen as she walks toward him. After a tearful embrace, Daniel asks her to marry him, and Nat joins the reunited lovers as they walk along the rocky bluffs into the sunset.