Hassan Salah (Héctor Elizondo), chief diplomat of the Legation of Swahari, an Arab nation with a new young king, has a scheme for shifting power within his government. He enlists Rachman Habib (Sal Mineo), a naïve idealist in the Legation, to help him stage the murder of a security officer, then plants evidence to make it look like the work of radicals. Salah pins the murder on the now-absent Habib, who, as part of the plan, has gone into hiding. Columbo quickly unravels the truth, but finds himself stymied by the fact that Salah has diplomatic immunity and cannot be arrested. Columbo then meets the new king, who is on a diplomatic visit to the United States, and impresses the young monarch with his down-to-earth personality. Columbo gets Salah to confess the murder with his monarch in the next room listening. To stay in the U.S. rather than face Middle Eastern justice, he waives his immunity from prosecution.

Jeff Goldblum, in his first TV role, non-speaking, is a protestor outside the embassy.