Higgins is preparing for a prestigious chess tournament, and the arrival of an important visiting dignitary, the President of Costa Del Rosa, who will be attending it. There have been threats made on the President's life, and Magnum is asked to apprehend those responsible. But both Magnum and Higgins have even more to contend with when yet another of Higgins' illegitimate half-brothers, the flamboyant Don Luis Mongueo, the last of the royal line of Costa Del Rosa, makes an appearance on the scene. But with the plots to assassinate the President, Don Luis emerges as the prime suspect.