After millennials of revolving around Mars, a massive asteroid called Pie is advancing toward Earth and will crash in eight years, which could wipe out humanity. As the world panics, the UN discusses the situation and allows China to form the Project United Nations Moon Shield or UNMS. The plan is to make a huge base on the Moon, build a super nuclear weapon called Cosmic Striking Hammers, use this weapon to destroy Pie, and use the Moon’s orbit as a shield to save Earth from the resulting debris.
Yue applies to go to the Moon and the interviewer isn’t impressed by him describing himself as a “middle man” and "average". Instead of an engineering position, he's offered maintenance. Desperate to go, Yue accepts and soon he's flying to the Moon with a whole crew of astronauts.
Eight years of hard work pass and the team finally launches the superweapon, which they happily celebrate. However Yue’s attention is on Lanxing, the base commander who he has a crush on. In his free time, he practices how he could confess his feelings, and he’s always there at the door whenever she comes back.
However Lanxing doesn’t even know who he is. Sometime later, Yue stays in his room listening to music while trying to write a good confession letter. Meanwhile Lanxing receives terrible news: a solar storm has caused one of the missiles to go off course and some asteroid debris has escaped the Lunar orbit.
In 27 minutes, those asteroid fragments will destroy the base. Lanxing immediately raises the alarm and orders everyone to evacuate. But since Yue has his headphones on, he doesn’t hear any of this and stays in his room.
All the astronauts rush to get in the evacuation rockets and finally abandon the Moon. It isn’t until Yue looks through the window that he learns about this. He immediately gets on a car and drives as fast as he can, noticing that all the rockets have left except for one.
Yue starts going faster as he tries using the radio, however the debris is too close and it gets in the way of the communications system. There’s a crater ahead and Yue tries to jump over it instead of avoiding it, but he ends up falling. At that moment, Lanxing launches the last rocket, leaving Yue stranded on the Moon.
Yue climbs out of the crater as the asteroid debris crashes on the Moon. He starts running around dodging the rocks to reach the base, which soon begins getting destroyed as well. Now Yue also has to dodge the falling pieces of building as the base goes down.
After being knocked down once, he tries to make a big jump to hide in the crater, only to be knocked down again. While he’s unconscious, a huge asteroid fragment makes its way toward Earth. When Yue wakes up, he starts complaining and tries to contact the UNMS.
At that moment the asteroid fragment finally crashes on Earth, causing a massive explosion that destroys a large part of the planet. Yue can only stare in shock and sorrow as he realizes their eight years of work were for nothing. Afterward Yue returns to the base and tries to contact Earth, but he never gets an answer.
For the following six days, Yue keeps on calling to no avail. He then realizes he’s the last human alive, which further pushes him into poor mental health. Using paper, he decorates a room for a pseudo-funeral to honor humanity.
The base still has food to feed 300 people and will last him a life time, so Yue decides he’ll do what he's always wanted to do. First he tries to get into Lanxing’s room, but he can’t guess the right password. Next he grabs a board and slides around the Moon just for fun.
As days pass, Yue keeps on trying passwords to the point of insanity. Eventually he gives up and uses an explosive to open the door, which blows up his clothes too. Now that he has access to Lanxing’s uniform, she creates a figure of her and prepares a whole dinner with romantic music to confess his feelings.
He even starts kissing the figure, unaware he’s being watched. It turns out there are survivors on Earth and now Lanxing is embarrassed in front of her colleagues. Civilians are in underground bunkers while the astronauts are in the UNMS underground base.
After some work they’ve managed to connect to the lunar base, but they can only watch Yue through the cameras without sound because the radio isn’t working. Because right now Earth is lacking resources, it’ll take them two years to fix the communication system and even more to rescue him. The UNMS chairman decides they can use this for good and shares an update.
The asteroid impact has fractured the planet’s plates, which has been causing tsunamis that flooded 30% of Earth’s land mass. Cities are covered in volcano ash and toxic gas, so soon there won’t be any plants or animals left. In the underground bunkers, people try to keep plants in jars but it’s hard to keep them alive without sunlight.
Diseases and depression are spreading among the survivors, who only get the most basic meals to survive. Some people are even losing their hair. The chairman thinks they should start livestreaming Yue’s life in the lunar base so survivors can get a glimmer of hope in these dire times.
Since they don’t have sound, they decide to hire a voice actor that can dub Yue’s voice to make him look heroic. Lanxing makes an announcement through the speakers to let all the survivors know that they’ve found a man on the Moon and that the stream will start in thirty days. Some people don’t believe it and suspiciously disappear.
A few weeks later, Yue is in a deep depressive state and decides to self-delete. He makes his way to the warehouse to get some medicine for the job and finds an open food package in the corridor that he didn’t drop. Yue opens the warehouse door and is shocked to see a beautiful figure lying down.
Thinking it’s a woman, Yue starts flirting as he comes closer, only to discover it’s actually a kangaroo left behind by the research division. At the same time, Lanxing starts the livestream so the first thing everyone on Earth sees on the screen is King Kong Roo. The voice actor they hired yells “What a fantastic day!
”, making it look like the kangaroo talked. To apologize for his mistake, the actor tries to play his flute, but that only gets him beaten up. Thankfully the survivors assume the audio is delayed and don’t think the kangaroo is actually talking, so Lanxing decides they’ll make the voice actor narrate instead.
On the lunar base, Yue reads the research regarding Kong, learning he’s aggressive and gluttonous, which is why he’s been raiding the pantry. He grabs a shovel and goes back into the warehouse to get the medicine. When Kong appears behind him, Yue waves the shovel only for it to break.
Then Kong grabs the handle and bends it before beating Yue up. Next Yue dresses up as a female kangaroo and tries to keep Kong distracted, but when he’s about to reach for the medicine, Kong brings him down and tries to do the naughty to him. This causes the mask to fall off and Yue gets kicked off the warehouse.
Moments later, Kong starts advancing into other parts of the base. Then Yue appears with a gatling gun that he just 3D-printed and opens fire, shooting plastic balls at Kong as he chases him around the base. However Kong suddenly turns around and starts chasing Yue instead.
As the voice actor plays his flute to make the scene epic, Yue and Kong start fighting each other hand-to-paw. After lots of struggle, they knock each other down at the same time. The UNMS is worried about him and ties to contact him again.
When Yue wakes up he hears some static on the radio. There are no words, but he cries because he sees this as a sign that there are survivors on Earth. What Yue and the UNMS don’t know is that the static was caused by Kong’s tail messing with the cables.
Yue and Kong stare at Earth as they realize they may have a chance to go home and they agree on a truce from now on, although Kong punches him anyway. Over two hundred days have passed since the incident and Yue never stops playing a message to try to contact Earth. He and Kong have found their routine, and Yue announces they’ve become a family.
Since it’s obvious that Earth won’t be coming for them, Yue decides to modify the spacecraft left by the old Apollo 18 Mission, hoping he can fly home on his own means. While people in the UNMS discuss if they can use this to help him too, Kong and Yue leave on the car and quickly find the Apollo. Yue runs a test and confirms it’ll work after some fixing.
The Apollo is brought back to the base and people on Earth watch Yue work hard on repairing it for multiple days. The UNMS is quite impressed so they check their profile, realizing he’s actually an engineer that somehow ended up in maintenance. Eventually Yue notices that Apollo can only carry 22 pounds, and Kong alone weighs more than that.
Feeling like he has no choice, Yue takes Kong for a ride and abandons him in the middle of the Moon. However Kong chases him and quickly gets back on the car. When they return, Yue starts researching a more powerful propulsion system and discovers that the prototype of the superweapon is still stored in the previous base.
Kong and Yue leave on the car with a bunch of supplies and only stop travelling at night because the vehicle requires solar power. It’ll take them weeks to reach the old base because it’s on the other side of the Moon, and people on Earth worry that Yue may not make it since the sun only shines on the Moon for fourteen days per lunar cycle. Soon the UNMS realizes Yue has been driving in the opposite direction to chase the sunlight.
The trip will take longer but he won’t get stuck. Now Yue has forty-one days to get to the base and can only sleep four hours per day. The first few days Yue and Kong keep each other entertained, but eventually the trip begins taking a toll on their mental health.
One day Yue wakes up to find Kong driving and talking, but this is just a dream. After accidentally driving into a crate, the duo finally makes it to the old base. Soon Yue finds the warhead and carefully brings it down.
Kong suddenly starts pressing a button repeatedly and Yue panics, but thankfully it’s just the inspection program. While they’re getting ready to go back, an angry Yue locks Kong up in the trunk to keep him away from trouble. Afterward he starts driving to the base, playing music as a distraction.
This stops him from hearing the trunk accidentally getting separated from the car. Hundred of miles later Yue finally notices the missing trunk, but going back for Kong would mean missing the sunlight. At first Yue drives away, but eventually the guilt is too much and he goes back to save Kong.
As everyone on Earth celebrate this decision, a happy Kong licks Yue to thank him. In the UNMS, Lanxing orders the entire team to find a way to contact an old lunar dog that was left behind by another mission, which hopefully could help Yue. At the same time, Yue and Kong keep on driving without stopping to sleep, otherwise they’ll miss sunlight.
After staying awake for over fifty hours, they notice that the sunlight is leaving them behind, but they don’t give up and speed up. The temperature starts dropping and Yue has to turn on the heat not to freeze to death, which consumes the car’s battery even faster. With only 35 miles left to the base, the battery finally dies and the car stops.
Yue gives up and comes out to wait for the end. In the UNMS, the team finally gets the dog to start moving, but it’s still too far away. They try making it jump over a crater as a shortcut, only for the dog to fall and break.
Back to Yue, he keeps thinking about Lanxing while staring at her picture on a mirror. Kong starts chasing the reflected light like a cat, giving Yue an idea. He rips off the car’s door and uses his tools to transform it into a sled, which he attaches to Kong.
Then Yue flashes the light ahead of them and Kong starts chasing it, moving the sled through the Moon surface. Eventually they find a big chasm and Yue makes Kong jump across it while activating some gas tanks that give them the necessary propulsion to make it to the other side. Everyone on Earth celebrates with hope and excitement, and there’s an award ready for Yue for when he comes back.
Humans gain more hope and work hard on fixing structures while signs of Yue and Kong decorate the bunkers. Thanks to this hard work, the UNMS only needs three months to regain communications with the lunar base. 516 days have passed since the incident and Yue is still working on connecting everything, which is harder than he thought because Apollo has outdated technology.
One afternoon, Yue gets excited because he finally hears static on the radio again. However when he turns to Kong, he finally notices him messing with the cables. Yue tests them with his own hand to be sure and his mind finally breaks as he realizes all his work and suffering has been in vain because he’s the only human left.
He yells at Kong for a while before the depression takes over his mood again. On Earth, the UNMS still needs a month to finish fixing the comms. Refusing to give up, Lanxing uses the speaker system to talk to all the people in the bunkers.
He admits Yue isn’t a hero, he’s an average man they left behind by mistake. But he’s been working hard to be a hero for a whole year, so he deserves people to support him in return. Lanxing asks the survivors to turn on their flashlights and shine them towards the Moon to tell Yue he isn’t alone.
At that moment Yue opens his helmet, and he’s starting to lose oxygen. However humanity comes together with flashlights and even lighthouses, lighting up the Earth to prove they’re alive. A shocked Yue falls to his knees in tears.
Finally by day 613, the UNMS fixes communications and Yue gets to see a human face again. After the initial celebration, Yue spends his days talking to the team, who has found the Apollo blueprints and guides him on how to connect the old technology with the new. Now Yue gets to see Lanxing everyday, and he thinks they’re becoming friends.
One night after they’re finally done with the repairs, Yue tells Lanxing that he initially turned down the maintenance position and left the interview. On his way out, he saw Lanxing and her smile made him change his mind. Moved by this confession, Lanxing makes one of her own: when she was evacuating, she did see Yue on the crater, but she left anyway because rescuing him would’ve killed them all.
She also admits she’d do it again. Meanwhile something in space is approaching Earth. The next day, Yue and Knog finally board the Apollo and get to leave the Moon.
There’s some turbulence at first but soon they make it to orbit and everyone on Earth celebrates. In just a few hours, the Apollo safely reaches the lunar station and Yue and Kong go looking for the escape pods. Unfortunately on Earth, they receive terrible news.
Another large piece of the asteroid that has been floating around the Moon has been pushed out of orbit by the rest of the debris and is now coming towards Earth. They’ve named it Pie Plus and it will destroy what’s left of humanity. The team realizes that the only one who can save them is Yue, who would have to pilot the warhead toward the asteroid with high changes of dying in the process.
Volunteering to do the talking, Lanxing contacts Yue while livestreaming the conversation. However Yue already heard everything because they left a mic on and he’s ready to do it because he wants to protect Lanxing and humanity. While survivors are told to hide in the bunkers, Yue cries as he shares an emotional goodbye with Kong before sending him back to Earth on an escape pod.
Afterward Yue takes off in Apollo and discovers there’s a field of meteorites on the way. Yue concentrates on piloting to dodge them as the Apollo gains speed, but unfortunately the ship gets hit anyway and begins spinning out of control with a broken thruster. Yue doesn’t know what to do but luckily Lanxing has a plan: he must open the door so the depressurization can compensate for the rotation momentum.
Sadly the door is jammed, so Yue starts kicking the hatch until it opens. This effectively makes the Apollo stop. At that moment Yue sees the ship’s engine floating away, meaning the Apollo doesn’t have power.
He has no choice but to move the warhead manually, but before leaving, Yue tells Lanxing he doesn’t blame her for leaving him behind and asks her to livestream his last moment. Then Yue leaves the ship and gets the warhead ready while offering a heartfelt speech as his goodbye to humanity. Everyone on Earth cries as Yue uses his jetpack to guide the warhead toward the asteroid.
While Kong’s pod lands in the ocean, Yue sings during his last minutes. The pressure of the asteroid destroys his suit yet Yue doesn’t give up and once he’s close enough, he asks a crying Lanxing to activate the explosive. A huge explosion destroys the asteroid and all the survivors come out of their bunkers to watch the meteorite shower that symbolizes they’re safe but also that Yue is dead.
Over ten years pass and humanity has been working hard on rebuilding Earth to make it beautiful again. There’s still much more to do, but at least now they can be outside in the fresh air. The chairman has retired, and Kong has a statue in his honor.
He also lives with other kangaroos in a reserve. Meanwhile Lanxing flies with a new group of astronauts to the Moon to clean up the old base. There she imagines that Yue is by her side watching the remains of Pie Plus forming a planetary ring around Earth.
