The Joseon Dynasty saw the height of classical Korean culture, science, and technology. Its reign is reknown for relative peace. However, that is all about to end when a group of assassins is hired to take out the king. This group consists of the best of the best, and they know exactly what they need to do to get to the king.

But with rumors about an assassination plot hanging heavy over the royal court, the king sends out his best line of defense. The Hwarang are specially trained warriors with a strict code of conduct. They are the most elite fighting force under the king's control, and his well-being is in their hands as they try to defend against these foreign attackers. As the assassins integrate into society, waiting for their chance to strike, the Hwarang must seek them out before it's too late.

When these two elite forces clash, chaos is bound to ensue. Honor is questioned, wills are broken, and hearts are torn apart as these supposed enemies realize that they're not so different after all.