For me this was a so-so drama, I thought this would be one of the competitors of Signal as a best mystery/crime drama but the story line is lacking for me because I find myself questioning some situations in the drama. The time travel concept was good at first but as the drama goes on they were not able to make me THAT interested on that concept anymore, it kind of seemed ridiculous to me during the latter. Though personally I am not a fan of Choi Jin Hyuk's acting even with the other dramas of his I've seen he was not that convincing and most of the time I ended up cringing during his scenes. I love Lee Yoo Young's acting here, most of her scenes gave me the creeps. The acting as a whole was great. This drama may be lacking in some parts but I think this deserves a try atleast.