Multi-billionaire Nathaniel Shepard, the influential CEO of Genesis, embarks on an unprecedented mission to colonize Mars. During this groundbreaking journey, astronaut Sarah Elliot uncovers the shocking news that she is pregnant. Tragically, after giving birth to her son Gardner on Martian soil, she dies due to complications, leaving the identity of Gardner's father a mystery. To shield Gardner from potential public backlash and safety concerns upon returning to Earth, Nathaniel decides to keep the child a secret, raising him with the aid of astronaut Kendra Wyndham and the rest of the scientific team on Mars.
Fast forward sixteen years, Gardner has grown up and, tapping into his remarkable intellect, he hacks into a robot he helped create to access his mother’s belongings. Among her items, he discovers a wedding ring and a video that features Sarah alongside a mysterious man in a beach house. Convinced this man is his father, Gardner is driven to locate him. Through an online chatroom, he connects with Tulsa, a savvy girl from Colorado's foster care system. Under the impression that Gardner is living in a luxurious penthouse due to a medical condition, they share dreams of their futures and Gardner promises to visit her one day.
In a video call, Kendra discusses Gardner's brilliance with Nathaniel and Genesis director Tom Chen, arguing for him to be allowed to visit Earth. However, Nathaniel adamantly opposes this idea. He believes Gardner would need risky surgery to improve his bone density and adjust to Earth's atmosphere. Defying Nathaniel’s wishes, Gardner undergoes the necessary surgery and training, ultimately boarding a shuttle to Earth, accompanied by Kendra and fellow astronauts.
Upon arrival, Nathaniel confronts Tom, revealing his anger over the fact that Gardner's training was concealed. As Gardner begins quarantine at NASA for medical evaluations, the results indicate he cannot withstand life on Earth for long. In a bold move, Gardner escapes to find Tulsa and enlists her assistance in his quest to locate his father. Hot on their trail, Nathaniel and Kendra attempt to bring Gardner back to NASA, yet he and Tulsa evade capture, eventually discovering Shaman Neka, the man who married Gardner's parents.
However, Nathaniel and Kendra soon discover concerning medical results indicating that Gardner's body contains dangerously high levels of troponin, signaling an enlarged heart—a condition that could be fatal due to Earth's atmospheric pressure. Gardner ultimately confides in Tulsa about his true origins, but she is skeptical. They locate Neka, who helps them track the beach house seen in Gardner's video, leading them on an adventure through Summerland, California, with a detour to Las Vegas, which quickly turns dire when Gardner collapses at a hospital.
After the medical team uncovers the carbon tubes in Gardner's bones, Tulsa finally believes his claims of being born on Mars. Aware of his deteriorating health and desperate to meet his father, Gardner enlists Tulsa's help to sneak out of the hospital. They arrive at the beach house, only to find that the man is actually Sarah’s brother—not Gardner's father. Overcome with emotions, Gardner retreats to the sea, expressing his wish to die there before losing consciousness.
In a race against time, Nathaniel and Kendra reach Gardner just in time to administer CPR, leading Gardner to inquire about Sarah, whereupon he realizes Nathaniel is indeed his father. In a desperate bid for survival, Nathaniel, Kendra, and Tulsa rush Gardner to a Dream Chaser spacecraft, launching him into orbit with hopes of stabilizing his condition. Freeing him from Earth’s gravitational pull restores Gardner’s health.
Eventually, Gardner embarks on his journey back to Mars after a heart-wrenching farewell with Tulsa. As Kendra looks to retire from NASA, she chooses to adopt Tulsa, who, fueled by her desire to reunite with Gardner, enrolls in Kendra's training program. The story closes with a glimpse of Gardner back on Mars, now with his father Nathaniel by his side.
