Ruler - Master of the Mask Episode 20

King who is upset after knowing the relationship between Ga-eun and Prince urges Queen mother to make her his concubine as soon as possible. Queen mother says Dae Mok will disagree to free her father's charge before putting her on the concubine position. 

Dae Mok tells Hwa-gun that the king has met the peddler's head and warns that if a person has a secret, even the most excellent person becomes a fool.

General Choi is back to the palace. Queen mother is wondering why Choi, who left the capital hating Pyunsoo, suddenly came back. Meanwhile, Choi finds out that the king is a fake.

Woo Bo tells King to become the master of himself before he becomes a king over his country in private conversation with the King. King also advises Woo Bo to stop doing something otherwise he will get hurt. 

Queen mother asks Ga-eun to find out what things the king receives from Pyunsoo group every month. Ga-eun enters King's bedroom at dawn, but soon she feels someone coming in. King hides her in his arm. 

King tells her to go away without looking back, asking her why she is trying to do something dangerous. She also wonders why King keeps helping her.

General Choi reveals the truth that current King is fake to Queen mother. He is willing to bring his entire army from the border to sweep out Pyunsoo group. 

Dae Mok who heard of the meeting of General Choi and Queen mother requests Hwa-gun to figure out the reason. 

General Choi then meets Prince and urges to attack Pyunsoo with his army, but Woo Bo says that will hurt numerous innocent people, so don't take that way to restore his throne. Prince agonizes between two.