There is a rightful holder of some position of authority -- the throne, the presidency, the chairmanship of a company, or something else. But someone with a lesser claim, or no claim at all, in some way manages to grab the position. The displaced and rightful holder may end up as Man in the Iron Mask, Noble Fugitive, The Exile. May cause a Civil War. Often appears with The Evil Prince or the Evil Vizier. Fiction being fiction, this is often bad, and it's usually Truth in Television as well, though for different reasons. See The Wrongful Heir to the Throne.