Commander Shen is eager to arrest the Duke of Jing An, so he locks down Tuozhou to ensure no one can return the painting before the Imperial edict is carried out. Man Qing returns the painting just in time but arouses Commander Shen’s suspicions. To go after the duke, he arrests the duke’s daughter for committing treason since she and Duan Yan knew each other previously. (Source: frankly at MyDramaList)