Started the series with high expectations given the synopsis and that Ji Sung is part of the cast. While the first half of the series was not without flaws, I believed there was an attempt to build up suspense (albeit slowly), which would be fine with me if the story built up well. Unfortunately, in the second half of the series, some characters seemed to display behaviour that seemed contrary to how they were written at the start, and developments became increasingly unbelievable.

For example, some characters seem to always escape the detection of the security despite acting in an overt manner, or how characters armed with pistols seemed to prefer hand-to-hand combat despite being in life-threatening conditions. This would lead one to wonder how these gaps would be closed as the story passes (hint: it does not).

We reach the rock bottom of the series in the finale, where the ending failed to address any of these plot holes and successfully created more questions on how a good 16 hours was wasted to watch this series. Like what some of the other reviewers pointed out, the acting fails to rescue the disastrous plot.