Evelyn, heiress to a West Virginia mining dynasty, is pregnant and deeply in love with her husband Damian. What she doesn't know is that Damian has been having a secret affair with her best friend, Serena. Together, they covet the core patent technology of the Harlow Group—the exclusive ownership of a new deep-well safe mining system. They conspire to lock Evelyn inside an abandoned mountain mine shaft scheduled for backfilling, intending to leave her buried underground, while telling the world she fell to her death. Before this, they had also plotted to kill Evelyn's brother, Wade—but Wade survived a fall into water and began secretly investigating their scheme. Trapped deep in the mine, Evelyn is utterly alone. The shaft is dark, collapses are frequent, and food and water are critically scarce. Her phone has only spotty signal. She survives on moss and rainwater, builds tools to dig a ventilation passage, and sends distress signals using a red sock, smoke, and tapping sounds. She endures nine days of hell—and gives birth to a daughter in the mine, only for the baby to be stillborn. Meanwhile, Damian fakes grief to deceive Evelyn's grandparents, Arthur and Eleanor. He tampers with the elderly man's oxygen equipment to harm Arthur, seizing the opportunity to obtain the patent transfer authorization. He prepares for a patent launch and engagement banquet, aiming to take full control of the Harlow Group's technological future.