Thomas Jerome Newton is an alien who has come to Earth in search of water to save his home planet. Aided by lawyer Oliver Farnsworth, Thomas uses his knowledge of advanced technology to create profitable inventions. While developing a method to transport water, Thomas meets Mary-Lou, a quiet hotel clerk, and begins to fall in love with her. Just as he is ready to leave Earth, Thomas is intercepted by the U.S. government, and his entire plan is threatened.