In the near future, an experiment gone wrong causes plants to start growing at high speeds
and gain mild intelligence. They begin attacking animals, but soon they move on people and start
taking over cities all around the world. After just one week, all that's left of society are
ruins and shelters. One year later, plants occupy more than 80% of the land area. Hao and his
daughter Yuan missed the last evacuation, and now they try to survive by living in the ruins. One
afternoon, Yuan finds a dog that reminds her of the pet she used to own and ignores her father's
warnings not to go after it. Hao worries because the sun is about to set and the plants come out in
the dark to attack, so he immediately goes after her. He finds her staring at a tree that has a
bunch of bodies caught on its vines, and Hao picks Yuan up to run away as the vines begin going after
them too. They rush through the woods and when the vines are about to catch them near the cliff,
they jump onto a large truck that they use as a bridge to go back to the place they
call home nowadays. Yuan wonders if she's being a troublemaker and if it had been better if her
mother had survived instead of her. Hao assures her she's doing fine, then he gifts her his watch
so he can keep track of her. Lastly he sings the happy birthday song until she falls asleep.
Afterward Hao goes back to use his radio to try to find other survivors and falls asleep in the
process. This causes him to miss two things: the plants are getting closer to the apartment,
and the Joint Forces send a message announcing a plan to reclaim Earth. Hao begins to dream about
the day of the catastrophe. He, Yuan, and his wife Yeyan had been stuck in traffic for hours,
and Yeyan wouldn't take her eyes off the computer because she was very worried about her project to
prevent desertification. Yuan didn't mind seeing her mom working because she saw this as saving the
world. Suddenly, they see people running away and birds acting weirdly. Yeyan gets a call from her
lab saying the plants they were working on began losing control. At that moment the ground starts
shaking and wounded people scream as they reveal there's a giant vine coming after them. Back in
the present, Hao wakes up when he realizes the screaming is coming from Yuan. The vines have
broken through the floors and are reaching for the bed, taking it and the girl away before Hao can
do anything. Yuan's still wearing the watch, so Hao wastes no time and goes back outside to track
her. The signal takes him to an old building full of plants, where he finds the watch on the floor.
Hao moves deeper inside while using a UV light to keep any plants away and finds a body on a chair,
but thankfully it's not his daughter. At that moment Hao hears Yuan scream and runs into
another room, where he finds her defending herself with a UV flashlight that is about to run out of
batteries. Hao throws his own flashlight at her, then tosses a piece of furniture to distract the
vines. Next Hao approaches the window, which has been sealed, so he begins hitting it to let the
sunlight in. As the vines begin closing around him, Hao finds a fire extinguisher on the floor
and throws it at the window, finally creating a hole big enough that allows sunlight to get inside
and scare the plants away. The vines drop Hao and he hits his head when he falls on the floor,
causing him to have more flashbacks. On the day of the catastrophe, Yeyan made the family return
to the lab so she could pack up her experiment. It was this testing that caused the plants to evolve
in the first place, but Yeyan thought she could modify the formula to weaken the plants and at
least make them weak to sunlight. She also pointed out that the plants were all connected to a root
network. The small plants in the lab were starting to react as well and suddenly a wall crumbled to
reveal giant vines that captured Yeyan. Hao grabbed her hands and tried to pull her back,
but more vines appeared through the door and grabbed Yuan, so Yeyan told Hao to let her go
and saved their daughter instead. In the present, Hao wakes up to discover the plants are trying
to take him. Suddenly a UV grenade falls on the floor and lights up the room, followed closely by
soldier Limo, who immediately cleans up the main vines and rescues Hao. Now the entrance is clear,
the rest of her team comes in and joins the fight against the plants. They all have plenty
of weapons, including a flamethrower, and while most of the team opens fire, Lei begins activating
the UVA radiator. However a vine takes him away, and 21 has to take over even if he doesn't know
how the radiator works. Captain Fang is almost grabbed too, but Yuan saves him by pointing
her flashlight at the plant. Hao notices 21 is having trouble and quickly joins him to offer
his technical knowledge, the radiator finally activates and emits a strong light that sends
all the vines away. Afterward Hao thanks the team and wonders what's going on. They explain they're
an operation team working for the Joint Force, formed by all the surviving soldiers around the
world to try to fight off the plants. Fang calls the base to explain their mission was delayed
because the reagent they're transporting was broken, so they came to the lab in this building
to fix it. Fortunately they find the necessary pieces and quickly begin working on fixing it.
While they wait, Fang shows Yuan a little magic trick, making a picture of her daughter appear
from behind Yuan's ear. Unfortunately he lost her during the catastrophe, making Fang wish he could
adopt Yuan instead, which makes Hao uncomfortable. 21 and Limo explain to Hao that scientists found
a huge root network underground that will end humanity when it breaks out, an event they call
"the green tide". There are fifty-four hours left before this happens, so various teams around the
world must find access to the root and inject it with hydrazide reagent, which will work as
a permanent plant sedative. These predictions are based on biological signals, and Hao tries
to point out Yeyan had discovered those signals are unstable and can't be trusted, but he isn't
taken seriously. Suddenly the building begins shaking and a vine breaks the floor, bringing
down the UV light and causing a few people to fall through the hole. The soldiers open fire in the
darkness of the room while on the floor below, Limo checks on Lei to find him severely wounded.
Hao and Yuan have fallen as well and notice a giant snake-like plant coming closer. This plant
is blind and hunts by following sound. The reagent fell away from them and Limo needs to retrieve it,
thus the trio decides to move as quietly as possible. Hao and Yuan manage to walk over the
plant's body without trouble and once they reunite with Limo, they finally grab the reagent, but this
accidentally moves some jars on the floor and makes noise. The plant turns around to go after
them and the trio runs to hide behind a table, but since the plant keeps coming closer, they have
no choice but to split. Yuan walks backward and accidentally hits a shelf that makes more noise,
causing the plant to go after her. Scared, Yuan runs away and ends up falling, so Hao and Limo
rush to put themselves between her and the plant. At that moment, Lei shows up opening fire on the
plant, and when the monster catches him, he tells the trio to run before activating a grenade to
bring down the plant with him. The force of the explosion forces the trio and the reagent out of
the building and shortly afterward, the rest of the team joins them. Because of Lei's sacrifice,
they don't have anyone to handle the reagent, and Fang asks Hao to be their new engineer. Hao
refuses because his priority is taking care of his daughter. Gui is furious because he sees Hao as
selfish, and Fang points out that if he doesn't come they'll die anyway, but Hao is firm on his
decision. Limo cuts in and says they should let him go, admitting she remembers what it was like
to lose her brother. The team begins going away, and Yuan announces she wants to join them because
her mother would've wanted her to help save the world. Now Hao has no choice but to come along
as well. As the group walks through the city, they come across a broken Ferris wheel, and Hao
tells Yuan that's where he had his first date with Yeyan, promising to take Yuan to an amusement park
after they save the world. This inspires Stone to ask Jing on a date after they save the world too,
but Jing turns him down. Stone doesn't give up and gives her a special good luck charm that his
mother made for him to gift his future wife, but Jing doesn't want it either and tosses it back to
him. Moments later, the weather starts changing again and all the birds in the area fly away. 21
receives a message from another team announcing the green tide is coming earlier than expected,
confirming Hao's point that the biological signs couldn't be trusted. As an earthquake hits the
area, a building starts to fall, and the group runs away just in time to avoid being hit. At that
moment, the green tide finally appears, although 21 points out this is just the beginning. The
group immediately begins running and finds a bus where they can hide, but Stone falls behind when
he's hit by a falling car. The earthquake opens a rift in the ground and Stone now can't rejoin the
team, so he runs as close as possible to the edge and throws the reagent at Jing before the plants
kill him. Limo has to come and grab a grieving Jing to drag her to the bus, but a vine stops her
by grabbing her uncle. Hao saves her by cutting the vine with a machete and the group finishes
entering the bus right before the earthquake and the vines begin tossing the vehicle all over the
place. The team has to be careful to protect the reagent and to grab onto each other until
they're all strapped to their seats. The pushing of the vines sends the bus flying off a cliff,
but fortunately the vehicle crashes against a building and gets stuck on the window,
allowing the group to get off safely. The team takes a moment to cry for Stone, especially when
Jing notices he left the charm on the reagent as a final goodbye. Fang notices he hurt his hand
during the bus escape, and Yuan thanks him for his protection by giving him a bandage.
Then Fang tries to contact the base to warn them about the early tide, only to discover they're
cut off. They need a signal booster, luckily there's a tower across the street. To reach it,
they'll have to cross a flimsy bridge that connects both buildings. The group begins walking
across the bridge very carefully, which includes having to sneak around a huge hole. 21 slips,
but fortunately he manages to hold onto the metal beams and keeps on moving by crawling.
Suddenly a building nearby begins crumbling, and while it doesn't hit the team, its fall sends an
air blast that pushes Yuan off the bridge. Fang reacts fast and using a grappling hook,
he jumps to grab her before she hits the ground. Hao tries to pull them up, but the weight is too
much and the bridge won't hold on for much longer, so Fang decides to do his final magic trick. After
telling Limo she's in charge now, he connects Yuan to the rope and then lets go to disappear into the
abyss. Other buildings around them are starting to collapse as well. The team hurries into the
tower and Hao pulls Yuan up to join them, throwing the girl at the soldiers before the bridge finally
collapses too. For a moment the team thinks they lost him, but Hao manages to hold onto the edge of
the window and Limo immediately pulls him inside. Minutes later, the team finds the main comms room,
and Hao fixes the generator to get power running again. 21 connects his computer and contacts the
base, but when Limo tries to inform them of the early tide, the commander reveals they already
knew about it because all the other teams are having the same trouble. According to their
new calculations, they only have four hours left. While the team discusses how to proceed, a message
from the High Command of the Joint forces begins broadcasting to the entire world. He explains
their scientists have discovered the root network has created a protective barrier on its periphery
using underground plants and microorganisms, meaning their reagent won't be able to penetrate
it. Since nuclear weapons aren't an option either because Earth can't withstand the effect anymore,
they've decided to cancel the mission. 21 uses an egg to explain how the protective barrier works to
his team, which gives Hao an idea. He takes over the conversation and gives the world a heartful
speech about all the loved ones that they've lost so far and the promises he's made to his daughter
on her birthday, begging for one more chance. The commander decides to let the teams vote,
and immediately all soldiers and bases around the world agree to try to finish the mission
even if the chances of winning are extremely low. Limo's team leaves the tower and crosses the city
to reach the launch station, which contains a gigantic drill. The green tide is coming closer,
so the team rushes to connect the reagent to the drill and send it underground. Unfortunately the
scientists were right and the drill can't break the barrier, the same thing happens to other
teams around the world. The plants begin attacking the stations and jam communications, and a sudden
noise announces the neighboring volcano is getting active. Limo explains this station is powered by
this volcano's geothermal energy through four sets of maintenance systems underground, and Hao
points out the volcano's magma could be used to destroy the barrier. 21 finds a map of the station
on the system and Gui finds a box of explosives, thus they agree to enter through the main access
point and blow up the whole maintenance system. Hao volunteers to go as well because he's the
only one that knows how to handle machines. Yuan begins crying, and Hao promises her he'll be back
soon. Gui, Limo, and Hao take the elevator to the access point, which 21 unlocks from the computer.
They can feel the heat as soon as they arrive, but when they enter the corridor, they discover
is full of plants. The trio immediately begins fighting, and in the struggle, Gui drops the bomb,
accidentally causing it to start the detonation countdown. A vine grabs Hao's leg and Limo cuts
it off, but now Hao's hurt and she has to help him walk. As the two of them move back, Gui decides
to follow Lei's sacrificing example, letting the plant capture him to activate a grenade and bring
it down with him. While teams all over the world give up and wait for the green tide to take them,
Hao and Limo reach the maintenance system. Hao sends Limo to find something to break the door
lock, but as soon as she leaves him, Hao opens the door with one of his tools and locks it
from the other side. Limo tries to open the door, reminding him this is her task, but Hao only asks
her to take care of Yuan before running away with the bomb. Crying her heart out, Limo runs back to
the elevator and reunites with the others to bring the bad news. The vines continue to make the whole
area shake and falling debris knock Hao for a few seconds, but he's woken up by a new broadcast
that tells humanity goodbye. Hao can't let that happen, so he drags his body to the final room in
the maintenance system and uses the security camera to say goodbye to Yuan, who is crying
and saying she doesn't want her dad to save the world anymore. At that moment, the bomb explodes
and allows the magma to come in, effectively breaking the barrier. The reagent finally
gets drilled into the root network, causing the plant to begin collapsing all over the world. As
humanity begins celebrating, the team leaves the station to watch the plant die, and Yuan
reminds everyone that this tragedy was a warning for people to start treating the planet better.