The murder (if that’s what it was) of Jamal Khashoggi in the Saudi Consulate in Istanbul, Turkey, was a horror in itself, and a greater horror still in what it threatens to unleash. The Muslim Brotherhood, Turkey’s President Recep Tayyip Erdogan and the ayatollahs of Iran are huddled over the corpse, hoping to turn a political profit from the death of an innocent man.

Mr. Khashoggi was a thorn in the flesh of the hyperactive crown prince of Saudi Arabia, Mohammad Bin Salman, a man who faces a concatenation of problems the...