In My Sister is The Warlord Queen movie, abandoned by their parents, the Blackwood sisters, Catherine and Grace, grew up with only each other to rely on. As adults, both built successful lives. But at Grace’s engagement party, Catherine shows up straight from an undercover mission, still dressed as a janitor, and becomes the target of ridicule from Grace's in-laws and former classmates. When her sister is betrayed and humiliated by her fiancé, Catherine reveals her true identity as the Warlord Queen, and makes everyone regret underestimating them.