Near midnight on March 16, 1792, King Gustav III of Sweden was handed an anonymous letter at a masquerade ball in the Royal Opera House in Stockholm, the building he had built himself. It warned that assassins were waiting on the dance floor. He folded it up and walked into the crowd anyway. Born in 1746 during the Age of Liberty, when the Riksdag even appointed his tutors, Gustav was taught by his parents to hide his true feelings, and his marriage in 1766 to Sophia Magdalena of Denmark was poisoned by his mother, Queen Luisa Ulrika, who spread rumors that Count Adolf Munck fathered the heir.

Taking the throne in 1771 amid the feud between the Hats and the Caps, each bribed by France or Russia, Gustav staged a bloodless coup in August 1772 with French money, then used his new power to abolish torture, curb the death penalty, and grant limited religious liberty. In 1788 he started an illegal war on Russia using soldiers dressed in Russian uniforms, survived the Anjala mutiny of his own officers, and turned the peasantry against the nobles to pass the Act of Union and Security in 1789. Enraged nobles, including Jacob Johan Anckarström, Adolf Ribbing, and Claes Fredrik Horn, then planned the shooting at the ball.

• The assassins wore black dominoes and white masks, and the pistol was loaded with two bullets and rusty nails.
• Gustav ordered the opera house doors sealed, governed from his bed for 13 days, and died of sepsis on March 29, 1792.
• His state vodka distillery monopoly was a spectacular failure among Swedes who distilled their own spirits at home.
• He was the first neutral head of state to recognize the United States, while profiting from the slave trade through Saint Barthélemy.
• His death inspired Verdi’s opera A Masked Ball, and his autocracy survived him until a new coup in 1809.