This is not Korean drama for beginners. In fact, the labyrinthine story is painfully difficult to follow and the narration goes to incredible lengths to keep the viewer off-balance and in the dark. Throughout the multitudes of characters, rarely is anyone portrayed as strictly good or purely evil. But the rewards for enduring this demanding watch are plentiful. There's no comedy. There's no snappy theme song. There's no happy hangouts at the tent bar drinking soju.

Kang Ha Neul plays Kim Yo Han, a young judicial trainee who is conscripted to help locate a valuable piece of intel for Kim Sang Ho's senior prosecutor. Things go wrong. Kim Yo Han ends up in prison where he's a pawn. Who are the real players pulling the strings? What are their plans for him? Neither question has a simple answer and even when it appears that a layer of illusion has been pealed back to reveal the reality of the situation, chances are that only a very small bit of truth has been unveiled. Kim Yo Han makes allies. And enemies. And sometimes the enemies later becomes allies only later to revert to enemies. And the allies are often only merely being used to further the revenge Kim Yo Han seeks.

Watching Kang Ha Neul play such a serious role is an enormous treat. He is easily among the most talented actors in the industry, with incredible range and a gift for delivering lines to maximize impact. Simply seeing him as Kim Yo Han is worth the mental fatigue from the brain-bending plot twists.

But to see Kang He Neul with a fellow lead that can match his talent? [chef's kiss] And Lee Yoo Young is exactly that. Her portrayal of Oh Soo Yeon, a fellow revenge seeker but one with a network of illicit connections, is both powerful and heartbreaking.

And there's more. Jung Man Shik is tremendous as a gang leader. Kang Yeong Seok is a mercurial gambler/prisoner that is both mentor and tormentor and a beguiling and simultaneously monstrous figure.

While the acting is as good as it gets, the writing and directing simply go too far to make "Insider" unnecessarily complex. Too many characters. Too many twists. Too many villains. Too many shady behind-the-scenes figures. Too many flashbacks to reveal the setup to what is about to happen. And as a result, Heo Sung Tae spends most of the show on the sidelines while pyramids of lower levels of setup gradually build to the point that he enters. And all of this excess means extra mental gymnastics when all that's needed is adding just enough color to the canvas behind Kang Ha Neul and Lee Yoo Young.

Put the spotlight on the talent. And then let them take over.

Highly recommended but with a warning that it's neither a casual watch nor for the faint of heart.