This drama was one of the best I have seen in 5 or more years. The concept and execution of the creation of a dual identify character (in a different timeline) that exists for the sole purpose of seeking revenge and ascertaining the culprits responsible for his murder (which was only attempted) was executed by the screenwriter with the highest respect for the viewers' entertainment and mental engagement. There were several times I had to go back and recount incidents to properly knit the story together to its final mindblowing conclusion. After watching episode 15 I was concerned that there was NO WAY this drama could have a good ending. However, I was totally surprised and enjoyed my Christmas day just screaming about how brilliant the screenwriters and directors were to lead to a 100% satisfactory and believable conclusion. The timeline changes were the hardest to comprehend but I used the weightlifter's silver metal (2004) event to account for the 20 years that passed to bring reality and the events of the last episode to a plausible reality as a viewer. Even the 10 years for the Miracle corporation converting into an arboretum was confusing at first -- you just have to remember that Do Jun died 10 years before the company basically removed itself from ownership of the Soonyang corporation. Totally satisfying and worth a rewatch if you are uncertain of timelines and events. A difficult watch but if you enjoy a challenge and a little eye candy to boot - this is one to watch.