Jordan Braddock, old billionaire owner of Braddock Industries, is flying toward a meeting in his private jet with his young wife aboard. The plane begins to have electrical problems, causing an emergency landing. Braddock isn't seriously injured from the crash landing itself, but the trauma has further complicated his already fragile health problems.
One of Braddock's vast corporate holdings is an automotive division, where a test driver named Ben Richards works. He loves being a test driver and loves his fiancee, Sylvia. He hears that Braddock is in town (but doesn't know about the plane crash) and wonders if the owner of the corporation will stop by for a visit. His co-worker says no, Braddock is just stopping by from "buying Chicago."
The two become linked by more than just faceless employer/faceless employee. Ben donated a pint of blood, which Braddock's doctor gives to the old man. While the news bulletins say that Braddock will soon die, inside his hospital room Braddock mysteriously becomes stronger -- strong enough to tear the arm restraints off and attempt to rip the oxygen tent apart. When Dr. Pearce makes his rounds the next morning, he discovers that Braddock has "recovered", and then some. He has cleaned out the floor of patients and replaced the hospital beds with desks. When the doctor asks Braddock how he feels, Braddock swears he's getting younger. Braddock thinks Dr. Pearce gave him some new "wonder drug" and, naturally, he wants to invest in it. Pearce swears he did nothing out of the ordinary but he has suspicions, which he keeps to himself.
Dr. Pearce goes to see Ben, the man who donated the blood that Braddock was given initially to buy the old man a few more hours of life. The suspicion is that something from Ben's blood caused the miraculous improvement in Braddock. Ben, when asked, says he's never been sick, not even with a cold or a sore throat. The other oddity, to Pearce, is that Ben's blood donor information lists him at 43 years of age. "You could pass for 30," Pearce says. After completing the tests, Pearce tells Ben that he has a fluke of nature. While everyone gets some disease immunities, Ben got them all. "As far as present life expectancies are concerned, you're almost immortal."
A problem soon arises: Braddock begins to age and get sick again. Pearce realizes that the effects of Ben's blood, when given to someone else, are only temporary. Braddock offers Pearce a $12 million research grant. Pearce rejects the idea because, since only Ben has the permanently rejuvinating qualities in his blood, he would be the target of any wealthy, powerful man who would seek to imprison him for the blood in his veins. Pearce knows how ruthless Braddock is and tries to warn him. Ben, however, is genuinely concerned with helping humanity and wants to be studied.
Ben and Braddock meet, but the meeting is less than cordial. Braddock wants Ben to get a less dangerous job, which Ben flatly refuses. After he leaves, Braddock tells Pearce that limits must be imposed on Ben to keep him safe (and, by extension, Braddock's chance at staying alive out of danger). Pearce listens without much comment as Braddock fumes over the possibility of Ben being injured from something as simple as walking across the street.
The next day, Ben disappears, kidnapped by Braddock's men and stashed away in a converted bomb shelter. Ben's car is found at the bottom of a ravine, the assumption being he died in a wreck. Pearce immediately realizes that Braddock has kidnapped Ben because of the remarkably calm demeanor Braddock is displaying over the supposed "death" of the man he wanted to have protected just the day before. Pearce cannot go to the police, however, as Braddock has shrewdly thought out that option and reminds Pearce that, if he goes to the authorities, he will have to tell them about Ben's blood.
While eating Ben finds a note in his soup. The note tells him there is a gun concealed on the serving tray. He finds the gun and escapes from Braddock's house. He escapes to Los Angeles.
Eventually he agrees to let Sylvia join him, but Braddock's men have tailed her to the airport and to the apartment building where Ben is living. They are chased up to the roof. Ben threatens to jump, and in response Braddock's men threaten to shoot Sylvia. She thinks they are bluffing, but they do shoot her, critically wounding her. At the hospital Ben asks the doctor tending to Sylvia to give her a pint of his blood, which the doctor reluctantly does. She improves almost immediately.
As Ben leaves the hospital he sees some of Braddock's men outside, waiting for him. A green Mustang pulls up alongside of him and the driver -- Braddock's young wife -- offers Ben an escape. Using his skills as a test driver Ben manages to elude the men following him.
Ben realizes now that everything Dr. Pearce tried to warn him about is true, so he leaves L.A. on a plane, leaving a farewell note to Sylvia: "I'm gonna miss you for as long as I live."