Gut-wrenchingly chilly, made me feel so suffocated! The acting and cinematography were so good that it gave me chills and made me feel so uncomfortable to watch this. I believe this is the best psychological horror serial killing drama I have endured to watch! Lee Dong Wook's smile was horribly enthralling and I was glued to my seat till the very last scene. I felt for Im Siwan and was so frustrated that no one helped him(his character) till the end. All the actors were amazing!