Story: The plot is very original and complex as it deals with themes such as human cloning and human rights. I think that the main question that is debated in this drama is if human clones have the same right to life as normal people. The beginning is pretty confusing as you're still trying to figure out the whole mystery behind the story, but every episode is very intriguing and it will make you keep watching. There is also some romance - even a love triangle, but it's not something too heavy. There was a second couple too which I didn't think it will work out in the beginning, but by the time it ended, I've started to really love them.
And about the ending... The way I saw it, I think they just left it open on purpose; everything would have been wrapped up properly if it wasn't for that last scene. In general, I can accept an open ending when they want to leave to the viewer's imagination what the future will bring for the characters, but not when they just throw another twist at the end and leave us with even more questions.
Acting/Cast: There are a few well-known faces in this drama and I was pretty content with their acting, but I was a little bothered by the main lead's reactions every now and then as they seemed a bit exaggerated.
Music: The songs that apperead in the background were all by Hurts and they've mainly used 'Stay' and 'Better Than Love'. It was an unexpected choice of music, but I don't think it was a bad idea because they matched well with the storyline. Also, they kind of give a more dramatic feeling to each scene, especially when they were played at the end of the episode.
Rewatch value: The thing with mysteries is that after you watch them once, your excitement just won't be the same because you already know what will happen. But I won't mind watching this drama again some time in the future.
Overall: There are a lot of good points to this drama - from the mystery that builds up each episode, to the intriguing circle of murders and the very touching moments between the characters. There are also some lacking points, but overall it's pretty good. If you're in the mood for a mystery drama with some psychological elements, this is perfect for you!