The film certainly does feature action, but most of it are snapshots of how regular people would fare or do when suddenly trapped in a building during a zombie epidemic and a straightforward tale of survival. The pov character is a random guy Joon Woo who very unfortunately slacked off on getting the groceries at the worst time. No particular special skills, but very online. The one time where the penchant to post personal information online works out as it turns out to be extremely important to the outcome of his survival. Also helping is that he's very lucky to happen to be living across from an outdoorsy woman Yoo Bin who still has all her gear despite the trauma she suffered from a fall three years ago. That's pretty much all we get to know about her aside from seeing her cleverly save Joon Woo from suicide with a laser pointer and tenaciously barreling through the zombies to get to him. The third and final resident survivor is a desperate husband in denial stage Bae Soo who drugs and tries to feed Yoo Bin to his zombie wife. That's a huge blow to the two of them who consider euthanasia and suicide by gun before the helicopters really show up despite them thinking Bae Soo was just lying to them. The government broadcast implies that Joon Woo's social media posts was what saved them as it was how the rescue copters knew which roof tops to look for them. It's unwittingly about a balance of hobbies, the gamer guy and the hiker girl, working together to get to safety.