The story opens when Tyler Dupree is twelve years old. Tyler and his mother live in a guest house on the property of aerospace millionaire E.D. Lawton and his alcoholic wife, Carol. Tyler is friends with the couple's thirteen-year-old twins Jason, a brilliant student who is being groomed to take over the family business, and Diane, with whom Tyler is in love. One night while stargazing, the three children witness all the stars simultaneously disappear. Telecommunications suffer as every satellite falls out of orbit simultaneously. Attempts to communicate with the ISS are unsuccessful.
An opaque black "spin membrane" has been placed around Earth. The membrane has slowed time so that approximately 3.17 years pass outside the membrane for every second within, or 100 million years on the outside for every year within. The membrane is permeable to spacecraft, and it protects Earth from the harmful effects of concentrated stellar radiation and cometary impact. A simulated sun on the inside of the membrane allows for a largely normal life cycle to continue. However, the passage of time outside the membrane means that all life on earth will end in a few decades when the sun's expansion makes that region of the solar system uninhabitable.
Jason becomes obsessed with gaining knowledge about the membrane and how to deactivate it. He studies science and eventually rises to run the day-to-day operations of Perihelion, an aerospace research firm that gets folded into the government and coordinates efforts to deal with the Spin. Diane joins the quasi-religious "New Kingdom" movement, a Christian sect that endorses hedonism and indulgence. She marries a man named Simon, whom she meets through the NK movement. Tyler attends medical school and becomes a doctor. Jason hires Tyler as a staff physician.
Perihelion terraforms Mars, a process that is finished in a few months of subjective Earth time. When the terraforming is complete, Perihelion and its counterparts in other nations launch manned colonization missions. Two years after the terraforming process begins, Earth receives satellite images confirming the existence of agriculture and sophisticated human civilizations on Mars. Soon afterward, Mars is enclosed in its own Spin membrane.
Before the membrane went up, the Martians sent their own manned mission to Earth. The Martian ambassador, Wun Ngo Wen, is part of a civilization hundreds of thousands of years old that has been experimenting with biotechnology for centuries. Jason, who has developed an acute form of multiple sclerosis that is incurable by terrestrial medicine, takes a Martian bioengineering product that extends his life by decades, putting him into a fourth stage of life past adulthood. Jason and Wun Ngo Wen then seed nanotechnology throughout the outer solar system. This technology will eventually expand to other star systems over the course of millions of years and search for other worlds enclosed by Spin membranes, hopefully discovering why they were created and if anything can be done to stop them.
Tyler leaves Perihelion and moves to California. There he gets a desperate call from Simon, stating that Diane is terribly sick. Diane and Simon had moved from the ashes of the NK movement to join a more cult-like fringe movement that was trying to hasten the second coming through genetic engineering of cattle. As Tyler heads to meet Diane, the Spin membrane seems to falter and fail, allowing the stars to return to the sky. The next day, the sun rises huge and red in the sky causing terrible heat and high winds. Millions across the world panic as the apparent end has come. Tyler finds Diane suffering from a fatal cardiovascular disease that crossed from cows to humans during the attempts by religious fringe to breed a totally red calf, which they think will bring out the end of the world. The only cure is to give her the same treatment that Jason has taken. He and Simon drive Diane back to Diane's childhood home where Tyler had hidden some of the Martian biotech. Simon, however, leaves Tyler and Diane and gives them his blessing, and is never seen again. Tyler discovers that Jason is at the house, dying of a mysterious ailment. Jason explains that he has become a human receiver for the nanotechnology they seeded throughout the galaxy. He also explains his conclusions about the nature of the Spin and the Hypotheticals who created it. The Hypotheticals are intelligent Von Neumann machines that spread throughout the galaxy billions of years ago. Horrified at the rise and fall of biological societies, they devised a plan to enclose planets on the verge of societal collapse in Spin membranes to slow their advancement until a way could be found to save them. Jason dies shortly after explaining this and has Tyler mail copies of the information to trusted informants.
Tyler gives the Martian treatment to Diane, who recovers. Shortly after, the membrane partially reasserts itself, allowing the stars to be seen and synchronizing Earth time with that of the universe, but filtering the solar radiation to a survivable level. It's discovered that the Spin membrane had been retracted to let a massive ring descend and embed itself in the Indian Ocean. The "Arch", as it becomes known, acts as a portal to another world, one engineered by the Hypotheticals to give mankind a new chance at life. A decade after the appearance of the Arch, Diane and Tyler, now married, flee from agents of the United States government who seek to arrest them for possessing forbidden Martian technology. Tyler takes the same cure that Jason and Diane did, becoming a "Fourth" himself, and Tyler and Diane pass through the Arch with a group of Indonesian refugees. They scatter Jason's ashes in the crossing between Earth and the other world so that he finally can be at peace.