In my opinion this is one of the best crime and paranormal dramas.
The drama is quite scary, especial the first episode, when they show what happened in the past.
As it progresses the drama also becomes quite emotional, and here the OST plays a big role. Somewhere is a very emotional song and it is played during the most important scenes.
The actors did their job very well. The most I liked Choi Yoon aka Father Mateo. I think Jae Wook did a great job in his character portrayal. Father Mateo impressed me the most because he was deeply hurt by what happened to his family, yet he was calm and considerate. It was touching how he protected Mi Jin's son from seeing his dead mother in episode 7, also how he took care of Seo Yoon. How he tried to protect her when the door opened and she got possessed, also how she treated her after, during her exorcism and after she was exorcised. Was impressive how she was sleeping on him when they were taking her home and how he was holding her hand. Felt like he took a special care of her. I think they have potential as a duo for a second season in which she chases spirits and he exorcises them. Also in last episode he was ready to die to save Hwa Pyeong when they were both in water. I think he also softened Gil-Young, by helping her understand that Hwa Pyeong also has his wounds. Hwa Pyeong was more reckless, but he was also ready to sacrifice himself to save Mateo. This was also impressive. However I think Father Mateo is one of the best characters i saw in a drama.