Mark Watney wakes up alone on Mars with an antenna shard in his abdomen, a failing EVA suit, and the realization that his crew has left him behind. He performs emergency self-surgery, assesses his supplies, and begins calculating how long he can survive.

Watney begins growing potatoes in Martian soil using crew waste as fertilizer and manufactured water from hydrazine decomposition. He transforms the Hab into a functioning farm, performing dangerous chemistry to generate the water his crop requires.

Satellite analyst Mindy Park discovers evidence that Watney is alive. NASA leadership — Teddy Sanders, Venkat Kapoor, Annie Montrose, and Mitch Henderson — grapple with the revelation, the public relations crisis, and the question of whether rescue is even possible.

Watney retrieves the 1997 Pathfinder probe from the Martian surface, restores it to functionality, and establishes two-way communication with NASA through an improvised system of rotating cameras and alphabet boards. Information flows between planets for the first time.

NASA rushes a resupply probe to launch, but it explodes during ascent. With no backup plan, China's space agency offers its own classified booster. International cooperation becomes the only viable path to saving Watney's life.

Astrodynamicist Rich Purnell calculates a trajectory that could slingshot the Hermes back to Mars. NASA rejects the plan. Mitch Henderson leaks it to the crew. Commander Lewis and the Ares III crew unanimously choose to extend their mission by over a year to rescue Watney.

Watney modifies his rover for a cross-continental journey to the Ares IV landing site at Schiaparelli crater, navigating power limitations, navigation challenges, and the psychological toll of weeks alone in a vehicle the size of a van.

An airlock breach explosively decompresses the Hab, destroying Watney's potato crop and severely reducing his food supply. The catastrophe forces a recalculation of every survival timeline and introduces genuine uncertainty about whether rescue can arrive in time.

Watney strips the Mars Ascent Vehicle to minimum mass, launches from Schiaparelli in a nosecone-less rocket, and the Hermes crew executes a desperate EVA intercept when the trajectories do not align. Commander Lewis catches Watney in open space, completing the rescue.