I'd been looking forward to this drama since it was announced and went into it really interested and excited. Unfortunately it didn't live up to what I expected.
Truthfully I wasn't really sure what to expect, but after the writers introduced the several plotlines in the first episode, I was excited to see what they would do, and then nothing really happened. Every single plot point (connect, organ traffickers, serial killer, etc.) was underdeveloped and didn't really go anywhere meaningful. Nothing was explained (I'm guessing they're counting on another season for that) and it just sort of ended.
I also had a hard time liking the characters, which makes it really hard for me to get into a series. The only person I did like was Ha Dong Soo, but even he was a little sad and pathetic that it was difficult to get fully onboard with him. Again, I think this is due to being undeveloped.
The actors did a good job, but I don't think they were given enough to work with. Or maybe it was just how the story was actually filmed/put together. I'm not really sure, but in the end the whole thing felt like it was missing something vital.