Dugu Yue, a former
flight dynamics engineer, is hired as a maintenance man for Project United Nations Moon Shield (UNMS), an operation spearheaded by the Chinese government which is intended to protect the Earth from an incoming asteroid named "
π". The plan is to deploy a group of new super missiles, called the Cosmic Strike Hammers, to shatter the asteroid and then use the
Moon to shield Earth from its fragments. Eight years after their launch, the Cosmic Strike Hammers successfully shatter "π"; but one of the missiles was thrown off course by a solar storm, leaving some of the asteroid fragments heading towards the UNMS Moon station. The facility is hastily evacuated, and in the chaos Yue is accidentally left behind. Arriving too late to board the last evacuation rocket, he witnesses one major fragment striking Earth, seemingly wiping out all of humanity. Considering himself the only human being left, Yue spends his time living out his unrequited crush on Ma Lanxing, his base commander, not suspecting that some UNMS operators, including Lanxing herself, have been watching him through the station's video surveillance feed. A portion of humanity has survived the disaster in pre-built underground bunkers, but Earth's situation is rendered desperate by a global dust cloud
blocking off the
Sun's radiation. UNMS chairman Sun Guangyang urges to establish a public
livestream link to the station in order to portray Yue as a role model and thus raise hope among the surviving population. Because the audio links to the station have been severed, it is decided to add
overdubbing and outside narration. Yue discovers that he has company in the form of a temperamental
red kangaroo named "King Kong Roo", left behind by the UNMS research division. Thus, the UNMS' first attempts to portray Yue as a survivalist go comically wrong as the two begin fighting over the station's food stores. During a brief lull, Yue notices some static sounds which leads him to believe that some people on Earth are still alive. He decides to reach some equipment left over from an 18th,
abandoned Apollo mission to reach the UNMS space station in the Moon's orbit and use an escape capsule to return to Earth. Yue begins repairing the
lunar lander, but to initiate liftoff, he needs the first Strike Hammer prototype, which is stored in another station at
Lacus Perseverantiae. Yue and Kong begin a journey on a solar-powered rover to obtain the prototype, and after several mishaps on the way, they make it back to the station. Yue discovers the static sounds were caused by Kong's accidental meddling, making him believe that he has apparently been living on false hopes. Despairing, he abandons his efforts, but Lanxing calls upon humanity's survivors to send him a combined light signal, thus telling him that he is not alone. With his confidence renewed, Yue establishes full audio-visual contact with Earth's UNMS headquarters, who help him in coordinating his repair efforts. In a private moment, Yue confesses to Lanxing that she was the sole reason for him to be hired on the UNMS mission, and a deeply touched Lanxing apologizes for leaving him behind. Yue finally completes the liftoff module and reaches the lunar space station, but just then the UNMS learns that another major fragment of "π", designated "π+", is on a collision course with Earth, threatening to completely annihilate all life on the planet. Overhearing the news, Yue volunteers to guide his lander towards "π+" so that the Strike Hammer's warhead can destroy it, but on his way there he hits leftover debris from "π", which disables the missile's engine. Knowing he is humanity's last hope, he heroically sacrifices himself by personally directing the warhead using his spacesuit's thrusters, destroying "π+". Over ten years later, after the dust around the globe has cleared away naturally, human civilization has rebuilt itself and even started advancing beyond its pre-impact levels. Lanxing returns to the Moon station, where she imagines being joined by Yue's spirit to watch the remains of "π+" settling in a stable orbit around the Earth as a
planetary ring. ==Cast==