Something that comes up almost as an aside in this handsomely mounted period piece, co-written and produced by Korean auteur Park Chan-wook, is the astonishing detail that, in the 16th century, invading Japanese soldiers would saw off their victims’ noses as trophies of war. So prolific were these ad hoc amputations that there’s a shrine of sorts in Japan — the Mimizuka monument in Kyoto, Tokyo — that holds the noses of nearly 40,000 Koreans killed during that time, not to mention some 30,000 similar “souvenirs” from China.

But, surprisingly, Kim Sang-man’s drama doesn’t play that card. This isn’t a story of Korea falling victim to outside aggressors, although that is a significant part of the drama. Instead, it’s a film about the enemy within, something the Koreans would know quite a lot about — most recently with corrupt president Park Geun-hye, whose secret 60-page document blacklisting Park and...