Marine Captain Jung-seok drives past a family pleading for help while escorting his own elder sister, her husband Chul-min and son Dong-hwan to a ship leaving South Korea. Once aboard, Jung-seok learns the ship is now being taken to Hong Kong. Before he can do anything, the zombie outbreak sweeps those aboard, including his sister and nephew. Jung-seok and Chul-min survive and settle in Hong Kong. Four years after the apocalypse, the two are sent along with two others Koreans to the peninsula on a mission to retrieve a truck full of money. They're promised half of the share if they make it alive along with the truck, but Jung-seok is initially reluctant. Seeing how this is affecting his relation with Chul-min, he agrees to go along. Once they land in the peninsula, they search for the truck and find it. Soon, zombies start chasing them but they manage to escape with the truck unharmed. However, on their way back to the Incheon port, the team is ambushed by a rogue militia group named Unit 631, led by Sergeant first class Hwang. Jung-seok is thrown out of the truck while Chul-min hides inside it. The female Korean dies. As zombies start chasing Jung-seok, he is cornered but rescued by two young sisters Joon and Yu-jin who leave the zombies behind, following a car chase. At their hideout, Jung-seok meets their grandfather Elder Kim and mother Min-jung. Jung-seok instantly realizes it was Min-jung he drove past while saving his own family. The truck is seized by Unit 631 after Hwang kills the remaining Korean who's slowly transforming. Chul-min is found inside the truck and in spite of his requests to set him free, is captured and thrust into fighting zombies along with other captured men in a gladiator-style game. On the other hand, Private Kim and Captain Seo subsequently discover the bags of cash in the truck and conspire to escape together, leaving behind Hwang and his team. Meanwhile, Min-jung learns of a ship at the Incheon port waiting to extract Jung-seok, and decides to steal the truck so that the five of them can escape. They arrive at Unit 631's compound, where Jung-seok and Min-jung neak sneak inside as the sisters and the old man wait for them in the car. The two discover the truck and encounter Private Kim. Jung-seok finds out that Chul-min is alive inside the compound and goes to rescue him. He ends up killing a number of zombies and Unit 631 soldiers, before Chul-min is shot dead by Hwang. Min helps Jung-seok escape by driving the truck away from the compound. They're joined by the sisters as they engage in a car chase with the zombies and Unit 631. The prolonged car chase results in Hwang and his driver getting killed.
A truck approaches a toll booth as it's being sanitized, with several workers cleaning the area in hazmat suits. The truck driver passes through the toll booth and accuses them of slowing him down, but the workers assure him that nothing is wrong, and that the area is just being sanitized as there was a small leak at a nearby nuclear plant. As he passes the toll booth, he is distracted by his ringing phone and accidentally runs over a doe. After inspecting the scene, he gets back in his truck and drives off. However, the doe staggers to its feet despite the crash and turns to reveal that it is infected. Meanwhile, in Seoul, Seok-Woo is a busy fund manager who barely has time for his daughter Su-an, let alone his divorce. After a stressful day at work and accidentally buying Su-an the same birthday present he did last year, Su-an reveals that she wants to visit her mother in Busan. Seok-woo is initially reluctant due to work, but his mother convinces him otherwise by showing him a video of Su-an singing Aloha 'Oe at a school recital (she stops singing in the middle of the song), which he couldn't attend due to work. Out of guilt, Seok-woo books the next KTX train bound for Busan the next morning. Early in the morning, Seok-woo drives Su-an to the station, only to nearly crash into an oncoming horde of ambulances and police cars. As Seok-woo ponders what could be going on, Su-an reaches out the car window and catches an ember in her hand, prompting Seok-woo to notice the burning building in the distance. He remarks that there's something bad going on, but drives to the station regardless. They board the train, which is also occupied by the tough working-class husband Sang-hwa and his pregnant wife Seong-kyeong, a high school baseball team, rich but selfish CEO Yon-suk, and a pair of elderly sisters, In-gil and Jong-gil, and a homeless man who seems to be aware of the zombie situation.
Once upon a time, the Trolls all lived in a tree, and they were the happiest creatures ever. They would sing, dance, and hug all the time. However, they were discovered by the Bergens, who were miserable and could only be happy whenever they ate a Troll. The Bergens gathered once a year for an event called "Trollstice", where they would eat Trolls and be happy for one day. Young Prince Gristle (voice of Christopher Mintz-Plasse) wakes up his father, the King (voice of John Cleese), on the day of Trollstice. All the Bergens gather around the Troll tree as Chef (voice of Christine Baranski) gets ready to cook up some Trolls. Since it is Gristle's first time ever eating a Troll, Chef prepares to hand over the happiest Troll, Princess Poppy (voice of Iris Dohrn). When she picks from the tree, Chef finds that all the Trolls have been replaced with wooden dolls with crazy hair. The Trolls have escaped underground to a new home, while the King banishes Chef from Bergen Town. She angrily vows to find the Trolls and have them eaten, while the King tells his son that nothing will ever make him happy. 20 years later, the Trolls live in the forest, with Poppy (now played by Anna Kendrick) leading them all in a song. Her dad Peppy (voice of Jeffrey Tambor) is king, and her Troll friends include Biggie (voice of James Corden), a big Troll with a worm friend named Mr. Dinkles; Guy Diamond (voice of Kunal Nayyar), who has an autotuned voice and can fart glitter; Cooper (voice of Ron Funches), a giraffe-like Troll; Satin and Chenille (voices of Aino Jawo and Caroline Hjelt), the fashionistas; DJ Suki (voice of Gwen Stefani); and Creek (voice of Russell Brand), a zen-like Troll. Poppy is throwing a party that day in honor of their arrival to this home. The only Troll that is never happy is Branch (voice of Justin Timberlake), who is grey and constantly pessimistic. He lives in a bunker to protect himself from the Bergens, and he refuses Poppy's invitation to the party.