Train to Busan is well acted, with many moments of surprising humor, has a great story, unbelievable drama, and fast zombies.  

Seok-Woo (Gong Yoo, The Age of Shadows, Squid Game) is a fund manager in Seoul, separated from his wife and lives with his daughter Soo-An (Kim Soo-Ahn). As a businessman, Seok-Woo does not spend much time with his daughter or show affection to her. On the night before Soo-An’s birthday, Soo-An insists on seeing her mother for her birthday, and having no other choice, he books a train ride to take her to Busan. Early the next morning, they board the KTX train for Busan at Seoul Station, but before train leaves, a distressed girl with a bite on her leg, makes it on board. No one notices her (or rather everyone is busy aggressively minding their business), but (unfortunately), she is infected with a horrific virus that is spreading like wildfire. A few moments later, she is the infected undead, biting and chewing her way through the train carriage, creating new zombies as she goes.  

As you can imagine, a metal tube is not the best place to be trapped during a rapid zombie outbreak and the only hope is for the surviving passengers to get to the front of the train and put a door, or a carriage between them and the infected. Seok-Woo, Soo-An and the other passengers on the train must now fight for their lives, as Train to Busan becomes a harrowing zombie horror-thriller that follows a group of terrified passengers fighting their way through a countrywide viral outbreak, trapped on a suspicion-filled, blood-drenched bullet train ride to the Safe Zone…which may or may not still be there.