Dr. James Xavier (Ray Milland) is a brilliant but unorthodox researcher whose work with human sight has yielded an experimental chemical that may vastly increase the range of what we can see.
Despite the misgivings and warnings of the two people closest to him, Dr. Diane Fairfax (Diana Van Der Vlis) and Dr. Sam Brant (Harold J. Stone), he uses it on himself and finds that he is able to look inside the human body in real-time. This gives him the ability to save the life of a patient in surgery, but in the process, he offends a top physician and calls his own judgement into question.
He won't stop or even slow his experiments, however, and when Sam is accidentally killed trying to stop him, he is forced to flee. Soon he is living the life of a hunted man, and is protected and exploited by Crane (Don Rickles), a larcenous carny-man who sets him up as a healer on skid row, taking peoples' pennies while Xavier makes his diagnoses.
After getting away from Crane, Xavier is found by Diane, who joins him on the run, and by now his own worst nature is coming to the surface. They head to Las Vegas, where his ability to see through objects allows him to win at most of the games in front of him, but he is discovered because of the attention that his streak draws to him.
Pursued out of town, he heads out to the desert, and by now his ability to see transcends the boundaries of earthly space, leading him to a terrible quandry and a hideous solution to his plight, inspired by an encounter with a preacher.