SOS是一种求救信号，传递紧急信息。僵尸世界大战bd1280

　　There is a fire in the classroom. There were two students in that burning classroom. 　　One died and one was taken to the hospital unconscious. Some say it was suicide and some say it was murder. Detective Eun-seob is staking out while the student is dying before he gets called in on the site. He witnesses the most terrible thing there.