A quite good thriller with an intriguing concept. The first half of the series was a bit slow and not that exciting despite the interesting thematic. The story required indeed at first introducing quite a bunch of characters as well as putting in place a lot of setup payoff. As a viewer, the second part of the show felt much more enticing as it was able to reap successfully all the elements built up in its first part.

Overall, the show became more and more addictive with each episode passing. However, it is to be noted that even though the excitement was picking up, unfortunately, the reveals were less surprising as most of them were predictable. What the series gained in terms of thrills, it also lost it as well in terms of freshness and unexpectedness.

Regarding the actors' performances, most of them were good (with a specific mention to Lee Joon Hyuk who really impressed me in his role). In my opinion, the only flaw in the casting was Kim Jee Soo: the actress did not exude enough charisma and I had real trouble believing in her acting...and therefore to be invested in her narrative arc.

One of the very strong points of the show was its grey characters. Nobody is really black or white and it is a pleasure to discover them layer by layer. It was also great to follow the two main leads forming a brilliant (and consistent!) duo. They were smart and making all over the episodes logical decisions. I was particularly happy to see a competent cop for once, quite an unusual sight in K-drama world.

Directing-wise, I loved some of the choices done around the concept of time and to exacerbate the mystery. I also found that the OST as well as the background sound were matching really nicely the drama.

I would recommend this to people looking for an original thriller with a fantasy twist and a nice ensemble cast. If you like novels from Agatha Christie, you could really enjoy this as well.