I enjoyed this drama throughout the entire 20 episodes, which is nice. I wasn't compelled to skip at all for fear of missing something important. It was interesting throughout. The only reason I brought it down was the over use of the typical KDrama tricks. Ridiculous situations that no one is dumb enough to fall for in real life but hep to further the plot. I understand why, but I don't like it. The acting was good. Although there was no really deep dive into any one character's emotions, it was still well done for an action story-line. Plus.... So Ji Sub. Since I watched this AFTER Oh My Venus, I was tickled to see another drama pairing up SJS and Choi Jin Ho. Also, was happy to see Im Ji Kyu again after seeing him in Suspicious Housekeeper. He's a cutie pie. The music got me. What an iconic song to use, Phantom of the Opera. (although I wonder how/if they got permission to use it). I thought the music supported the action very well. It was a good match. For rewatch value I score slightly lower, only because I feel like I didn't miss anything or have any confusion that would require me to revisit things. Although the plot was complex, it was explained clearly so I wasn't left scratching my head. I recommend this for anyone who loves a good mystery, suspense and issues that are neatly resolved (either good or bad) in one episode. If you are looking for a gratuitous So Ji Sub body shot...go watch Oh My Venus. You won't find it here.