Part of the appeal of Yeon Sang-ho’s 2016 horror hit Train to Busan was its modest ambition: Nearly the entire movie takes place on a commuter train from Seoul to Busan as a zombie outbreak slowly spreads among the passengers. It’s basically impossible to come up with a new twist on the zombie genre, but Yeon executed the familiar elements well, demonstrating a flair for staging exciting action sequences even in a confined space.

Yeon’s new sequel, Peninsula (cumbersomely titled Train to Busan Presents: Peninsula for its U.S. release), follows in the tradition of many sequels to surprise hits, vastly expanding the scope of the story while struggling to replicate what made the original so successful. At first, Peninsula seems like it might offer a variation on the original movie, following military officer Jung-seok (Gang Dong-won) and his sister’s family as they board a ship to escape South Korea, which has been overrun by zombies. One infected person makes it onboard, which looks like the set-up for another confined-space horror movie on a boat rather than a train.

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But that attack is only the prologue to the real story, which takes place four years later. None of the characters from Train to Busan show up here, and anyone who hasn’t seen the original movie will be quickly caught up via some awkward talking-head exposition from TV commentators. That TV commentary is one of a few instances of English-language dialogue in what feels like a concession to the international audience that the movie is aiming to reach, but zombies are a universal language and having a few scenes in stilted English doesn’t really make a difference.

In the years following that ill-fated boat trip, other countries have closed their borders to South Korean refugees, and the Korean peninsula has been shut off from the outside world, containing the zombie outbreak within. Jung-seok’s sister and her young son died on the boat out of South Korea, but Jung-seok and his brother-in-law Chul-min (Kim Do-yoon) made it to Hong Kong, where they’ve been living in undocumented limbo. A sleazy American businessman approaches Jung-seok, Chul-min and a few other Koreans with a proposition: Sneak back into the country to retrieve a truck full of American cash and they’ll be rewarded with half of the multimillion-dollar take.

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Jobs like that are always too good to be true, and almost immediately after landing in the port city of Incheon, the group is beset by zombies and by violent groups of citizens who were left behind after the evacuation. With their compatriots dead and the truck stolen, Jung-seok is rescued by a pair of scrappy kids with some serious driving skills, while Chul-min is kidnapped by the vicious Unit 631, a former military rescue unit gone rogue. And the clock is ticking as the boat that brought the group from Hong Kong to Korea is waiting just off the coast for only three days, after which Jung-seok and Chul-min will be permanently stranded on the peninsula.

All of Korea has descended into complete post-apocalyptic chaos over the course of four years, and Yeon draws from dystopian sci-fi influences like Escape From New York and the Mad Max movies as much as from the zombie genre. The zombie threat here is more about hordes of ravenous monsters than it is about a single bite or one person slowly turning. Early on, there’s some inadvertently relevant social commentary when Jung-seok and Chul-min are harassed in Hong Kong, where people regard Koreans as virus carriers, but for the most part Peninsula is about nonstop action and suspense rather than allegory.

The action is excellent, with Yeon using all of the expanded resources at his disposal thanks to the success of the first movie. The epic climactic car chase, featuring a caravan of vehicles racing to get to the port to meet the boat, is worthy of Mad Max: Fury Road, and an earlier car chase featuring those quick-reflexed kids could have come from a Fast and Furious movie. Meanwhile, Unit 631 forces Chul-min into a combat arena in which scared prisoners must fight off zombies. Between all these elements, it's like Yeon is checking off boxes on a post-apocalypse bingo card. Yet, even as he relies on clichéd plot points, Yeon executes each one with maximum intensity and excitement, just as he did in Train to Busan.

Like Train to Busan, Peninsula mostly falters when it comes to character development, burdening Jung-seok with obligatory redemption on two fronts. He feels guilty about holding Chul-min back while Chul-min’s wife and son succumbed to the zombie virus and he also feels guilty about refusing to help a stranded family while on the way to the initial rescue boat out of Korea. Coincidentally, it is the kids of Min-jung (Lee Jung-hyun), the mother of that family, who rescue Jung-seok from attackers, and so he feels duty-bound to save both Chul-min and Min-jung’s family.

At nearly two hours, Peninsula drags on too long, and Yeon leans too hard on the emotional melodrama, with cheesy, overwrought music accompanying moments of anguish and heartbreak. Gang is a capable leading man, both as an action hero and as a conflicted leader, but Jung-seok is a dull, upstanding protagonist. The devious supporting characters, including Kim Min-jae as a deranged Unit 631 sergeant, are more entertaining, but the main focus remains on the impressively staged action. Given greater resources, Yeon has put together a large-scale spectacle worthy of his wider audience.

Starring Gang Dong-won, Lee Jung-hyun, Kim Do-yoon, Kim Min-jae, Lee Re and Koo Kyo-hwan, Train to Busan Presents: Peninsula opens Friday, August 21 in select theaters.

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