Thomas Jerome Newton is the man who falls to earth. He comes from an alien planet which is slowly dying from a lengthy drought, and has left his wife and two children in the hope of finding a solution on Earth.

Arriving in Haneyville, a small village in the Southern USA, he sells his wedding ring for twenty dollars. Over time, he becomes increasingly powerful, using skills from his planet's advanced technology to create seven patents which will make him a multimillionaire and allow him to compete with many big American corporations. He hires a patents lawyer, the myopic Oliver Farnsworth, to act as president of his company, World Enterprises.

World Enterprises becomes one of the biggest players in the international business market and diversifies into publishing, advanced photography equipment and mineral resources.

Meanwhile, Dr Nathan Bryce, a libidinous college professor with a penchant for eighteen year-old girls, is becoming fascinated with World Enterprises, having been shown a reel of self-developing film by one of his many lovers. For a year he devotes himself to pursuing young women and researching World Enterprises, having realised that his position as a teacher is becoming untenable due to his lack of interest.

Newton, becoming reclusive and obsessive, travels to New Mexico, where he stays in a small hotel. Becoming seriously ill during the journey, he is assisted by Mary Lou, the hotel maid, who takes a liking to him and shares stories of her inconsequential life. His need for regular drinks of water becomes clear but Mary Lou prefers to drink gin and persuades Thomas to join her in her habit. Newton asks her to bring him a television, something he immediately becomes fascinated with.

Some time later, Newton moves in with Mary Lou, spending his time drinking and watching multiple television sets. The more he watches, the more paranoid he becomes and his relationship with Mary Lou begins to break down.

Newton is somehow psychically linked to Nathan Bryce, listening to his lovemaking and his obsession with World Enterprises. Bryce, unaware of this connection, gets a job as a research chemist with the Corporation and is initiated into its obsessively secret world. He meets Newton and is shown a prototype space capsule which will launch World Enterprises into the space program. Farnsworth, alarmed by this development, is approached by a mysterious Government agent named Mr Peters, who informs him that the powers of industry and government will not allow Newton to successfully launch into space.

Newton becomes increasingly lonely, yearning for his alien wife and children. He reveals his true alien nature to Mary Lou, appearing before her without hair, nipples or genitals and with his 'human' contact lenses removed. She is terrified and seeks refuge in alcohol, eventually being paid to leave Newton by the government, who are gradually removing all links between Newton and the outside world - including Farnsworth, who is thrown from his top floor apartment. Newton tells Bryce about his true identity, revealing that many visitors from his planet have come to Earth before but have not been recognised.

Newton's space project is sabotaged by the government and he is imprisoned in a luxurious penthouse, where he is examined by doctors who seem persuaded that he is really human, either a freak or a fraud, despite his protestations. They also expose his eyes to X-rays, causing his contact lenses to become permanently fixed.

Time goes by but Newton seems immune to the aging process. Mary Lou finds him with help from Bryce, and she and Newton make love and drunkenly play with a gun filled with blanks. Newton yearns for an end to his misery but finds solace only in drinking. His alien family, now unable to communicate with him, die of thirst on the barren planet. He escapes from his luxurious prison but discovers he has nowhere to go.

Many years later, Bryce and Mary Lou have become lovers. Bryce meets Newton but lies about his relationship with Mary Lou, the second woman whom Newton has loved and lost. Newton claims not to be bitter about his imprisonment on Earth.