I'll start by saying it's a shame there are a lot of negative reviews about this because I actually enjoyed the series and I don't regret watching it, in the first few episodes I was quite confused but then things did start to pick up and aspects of the plot got more interesting and quite exciting. However, the reason I didn't score higher is because I did have some issues with the series.

As other people have said, there are a few plot holes that never get fully explained, but that doesn't really detract too much from the enjoyably of the show, yes it was disappointing to see that lack of detail in the writing, but I personally didn't mind as much. There were many exciting moments that had me at the edge of my seat, and if you view the series as a crime thriller/ suspense/ murder mystery rather than a supernatural series, then you can see it is actually quite good, except for the ending, but i'll get to that in a bit.

I think the main reason people criticised the plot was because of how they did the supernatural elements. The whole thing about how Cha Min gets the abyss just seems a bit pathetic to me, and the fact that the ones that give it to him never reaper throughout the rest of the series (except the tiny bit at the end) doesn't make sense. I don't get what people are saying about Abyss not being relevant to the plot when it is shown or talked about in every episode, but I can understand their frustration on how it was never really explained about very well.

The REAL problem with the series was the ending!!! it seemed like such a forced scramble to make sure they had a happy ending that seems as if they put no thought into how it would end. Don't let that put you off watching but just be prepared for a really stupid last episode, they seriously could have done so much better with that. I think it would have been better to finish on a cliffhanger with the trial still going, (it was far to quick to be realistic) and "someone" still missing (I'm trying to avoid too serious spoilers here) then have a second season to fully flesh out all those plot details and have a better conclusion for the characters return, instead of it simply being 'oh hey i'm back, I missed you, this is what happened'.

One other thing I would have loved to see more of is the developing relationship between Cha Min and Se Yeon in the past not just their romance as adults. I would have liked to have seen more flashbacks of them becoming close friends as kids, and how Cha Min was there for Se Yeon instead of just repeatedly telling us that they were childhood friends.

Now onto the true saving grace of the series that made me enjoy watching.... The cast!

The character portrayals in this series was amazing, hats off to the casting director because the actors really play their parts beautifully. I'm a big fan of Park Bo Young and I think she is a brilliant actress and can really deliver the emotion her character is feeling. This is the first thing I have seen with Ahn Hyo Seop and I will defiantly go check out more of this work no I have seen this. And the rest of the cast too, Lee Sung Jae, Lee Si Eon, Han So Hee and Kwon Soo Hyun all portrayed their roles so brilliantly it just goes to show that the cast can really make the show, even if people had a problem with the plot, it can't be denied that the actors did a great job.