What. A. Movie.
I was skeptical about this movie but decided to give it a try anyway and I can say with no doubt that I have absolutely no regrets.The movie pulls you in right from the beginning and keeps you on the edge of your seat throughout until the end. The story, screenplay, characters, everything was so well written. The acting was top notch as well. Wi Ha-joon was outstanding as the serial killer and Jin Ki-joo playing the deaf protagonist did such a great and convincing job with her acting and sign language conversations. Even the supporting actors were fabulous.
The movie did come with it's fair share of plot-holes and frustrating moments(extreme ones at times) but the viewer wouldn't even think of any of that by the end of the movie. One could also argue for it as part of cinematic liberty.
Overall, this movie is easily one of the best thrillers out there and is absolutely a must watch.