The lead actors performances are what really elevate this drama and make it better than what it really is. The way they capture the sorrow, the pain, the fire, the determination of their characters is superb. I've never seen Moon Geun Young in any other dramas, just a couple of rom-coms from her younger days (both of which are utterly delightful), so I have no experience seeing her in this sort of role, but when you watch her dig through a practical mountain of garbage while sobbing her eyes out because she's so desperate to find her sister, that can do nothing else but hit you in the gut. As for Kim Seon Ho, the only other project I've seen him in is Strongest Deliveryman (where he almost steals the entire show, his performance is so good), and he seems to have a particular talent for taking his characters and making them feel Real.

And that's really why I finished this drama. There were a lot of things I enjoyed about the story, but nothing that would have kept me watching if the leads hadn't been so well-portrayed. The mystery, as invested in it as I was at the beginning, really struggles in the middle, and while the conclusion gets some things right, it also gets some things wrong. The case of the day format sometimes works and sometimes doesn't (although that's something I think could have been overlooked if the over-arching mystery had been a little better). And the biggest flaw/frustration of the drama for me was Ma Ri. She's unnecessarily aggressive toward the female lead and makes some Really dumb decisions in relation to the central mystery because of it.

This is a drama that does some things well and some things not so well. I would suggest, if you're looking for a drama where the crime/mystery element is really compelling and well-paced and well-written, that you maybe look elsewhere. But if you like dramas with compellingly portrayed leads, then this is definitely a good drama to watch.