The story line is rather interesting and thrilling but there are some brutal scenes that are difficult to watch. The actors/actress that play as Moo Jin Hyeok and Kang Kwon Joo perform well and make the "Voice" exciting to watch from the first episode to the end. Some side stories that is interrelated to the main story line. "Voice" could be shortened to 12 episodes since there are too many scenes that are repeated here and there. The good thing about this K-drama series is that it sticks to its core of the story and no "love scene" or "sexual attraction" between the two lead characters. The one that is difficult to stomach is that when we find out that Shim Dae Shik is the "mole/rat", it is typical K-drama series that the least expectant person is the "mole/rat".