Ten years have passed since a solar flare destroyed the ozone layer, increasing temperatures to 150 degrees Fahrenheit (70 degrees Celsius) and turning the planet Earth into a largely-uninhabitable wasteland scorched by ultraviolet radiation, and subject to extreme weather events. One of the few survivors, robotics engineer Finch Weinberg, lives alone with his dog Goodyear and a helper-robot Dewey in an underground St. Louis laboratory once owned by the company he worked for before the cataclysm. Finch only ventures outside to search for supplies with a heat and ultraviolet-resistant protective suit.Dying of an undisclosed ailment (though Finch is seen reading a book on radiation poisoning), Finch is working on creating a more advanced humanoid robot companion to take care of his dog once he is gone. Finch feeds it volumes of encyclopedic knowledge, including a manual for training and caring for dogs. However, Goodyear initially doesn't trust the robot (which eventually chooses the name Jeff.)When a massive storm approaches St. Louis, and it is predicted to last 40 days, Finch, Jeff, Dewey, and Goodyear set out in a heavily modified motorhome towards San Francisco. Because of the hasty departure, only 72 percent of the data could be uploaded to Jeff, also he has the mental capacity of a child. Despite his condition worsening, Finch tries to teach Jeff some valuable lessons about life and how to protect Goodyear. Jeff's inquisitive behavior both amuses and frustrates Finch, and as Jeff shows more initiative, he inadvertently stumbles into a trap which destroys Dewey, and their motorhome is pursued by an unknown car. However Finch forgives Jeff after he helps their vehicle from being overtaken, in spite of a panicked error in judgment by Finch.Approaching their destination, the UV radiation has dropped low enough for Finch to be able to step out into the sunshine without a protective suit. He spends an afternoon outside with Jeff, teaching him how to play fetch with Goodyear before quietly dying. Jeff and Goodyear make their way to San Francisco, finding the city habitable but deserted, and set out to find any surviving humans.