Lady of the Court(1972)

Original title: 궁녀

When King Myeong-jong dies, his son takes the throne and the old king's concubines are expelled. One of the concubines becomes pregnant. Believing that only she knows the true father, she claims the unborn child is the former kings and has a claim to the throne. The enemies of the new king, ignoring facts, decide to support her claim and threaten to start a civil war.