"Overdo" tells the story of Murong Qingyi, the youngest son of a warlord family in Republican-era Shanghai, who suffers abuse from his adoptive father after being switched at birth. When he escapes as a young man, he is saved by Ren Susu, but his involvement brings disaster upon her family, causing its downfall. Years later, the two reunite and secretly develop feelings for each other, yet Ren Susu resolutely fakes her death and disappears to save others, leaving Murong Qingyi to sink into the pain of losing love. Three years later, Ren Susu returns, only to become Murong Qingyi's future sister-in-law. Now, one carries deep resentment from betrayal, while the other hides an indescribable pain. Between suspicion and struggle, their love and hatred become intertwined. As misunderstandings are gradually cleared and their love reignites, a national crisis arrives. With the determination to face death in their fight against enemies, where will the fate of Murong Qingyi and Ren Susu lead?