The movie wasn't good but it also not bad. It was something maybe I could watch in the background while doing some laundry. It was a textbook "serial killer" movie. The stalking, thinking the victim initiated it and the memorabilia, but what it lacked was any information about who the killer. The build up is that the true identity of the killer is the detective's son, but it turns out that he was his victim.
The character arch of the female lead made no sense, she was the quiet, every-woman and (I am using this term quiet often because that is the exact opinion I felt) but suddenly she becomes this badass strong avenger.
And the cherry on the top. No character dies. Yes there are deaths of his previous victims but no character we are introduced to dies. The father who she thinks dies, doesn't so...... it becomes a happy ending(this is a personal choice, I need me some misery).
I have been going on about what is bad, but there are two good things:-
1. Im Shi Won - though his acting skills could be challenged in much more way( again, though he was great, his acting was average.
2. The POV of the phone - the movie has multiple instances where the POV that the audience gets is that of the phone which is a cool cinematographic quirk,