Anna and the Apocalypse

In Little Haven, Scotland, Anna Shepherd is about to finish school. She plans to travel for a year before going to university, much to the displeasure of her widower father, Tony. Her friends are dealing with their own issues: her best friend John, an artist, is secretly in love with her, budding filmmaker Chris is struggling with a class assignment and transfer student Steph is trying to get her social justice reporting past the tyrannical vice principal Mr. Savage. Nick, Anna's one-night stand, is also making her life difficult. On the night of the school Christmas show, in which Chris's girlfriend Lisa is performing, Anna and John work in the local bowling alley, and Chris and Steph go to the homeless shelter to film Steph's story. During this time, a zombie infection starts spreading.
The following day, Anna and John leave for the school, completely oblivious to the zombie chaos around them. When they encounter a zombie dressed as a snowman, Anna decapitates him with a seesaw. At the school, a group of adults, including Chris's grandmother, Mr. Savage, Tony and Lisa, are taking refuge. Tony and Mr. Savage argue about whether to save the other survivors outside or lock the doors and stay inside the school, with Mr. Savage winning the argument with a sudden military broadcast. Figuring it will be too dangerous to go home or to school, Anna and John go to the bowling alley, where they meet Steph and Chris, who have taken shelter there. Steph discovers an army evacuation is coming to the school, so the group plans to go there once it is safe. Steph kills the zombified janitor, which alerts a group of zombified bowlers to break in. The group kills them all after a bloody fight, and they realise that getting to their loved ones will be difficult.
The next morning, Anna, Steph, John and Chris wake up to find that the army has been zombified and no evacuation is coming. Regardless, they set off to the school to see if their loved ones are still alive. Nick - immensely enjoying the carnage - and his friends rescue the group from a horde of zombies and join them on their way to the school. Anna tells John that she still plans to travel despite everything that has happened. She also notes that he is her "best friend", implying she knows about his feelings but does not reciprocate. At the school, Savage fights to maintain authority as the others plan their evacuation.
The students are ambushed by zombies, which kill Nick's friends and bite John; he gets Anna to safety but sacrifices himself to distract the zombies. The survivors reach the school, where Savage has let the zombies in as a last-ditch measure of control. Anna and Nick split off to search for Tony while Steph and Chris look for his family and Steph's car keys. A group of zombies separates Nick and Anna. Chris finds Lisa, but his grandmother has already died of a heart attack. Steph, Chris and Lisa find the car keys in Savage's office, but Chris and Lisa are bitten while trying to escape.
Anna finds Savage in the auditorium, where he is using Tony as bait for the zombies. Anna frees Tony, but the two men fight. Savage falls to the zombies, and Tony reveals he's been bitten. Nick arrives in time for Anna to bid her father goodbye. They prepare for one last stand before Steph rescues them in her car. Anna finally leaves Little Haven to look for a safe place.