The Mayerling Incident

The Mayerling Incident is the series of events leading to the apparent murder–suicide of Rudolf, Crown Prince of Austria (21 August 1858 – 30 January 1889) and his lover Baroness Mary Vetsera (19 March 1871 – 30 January 1889). Rudolf was the only son of Emperor Franz Joseph I of Austria and Empress Elisabeth, and heir to the throne of the Austro-Hungarian Empire. Rudolf's mistress was the daughter of Baron Albin Vetsera, a diplomat at the Austrian court. The bodies of the 30-year-old Archduke and the 17-year-old baroness were discovered in the Imperial hunting lodge at Mayerling in the Vienna Woods, fifteen miles southwest of the capital, on the morning of 30 January 1889.

The death of the crown prince had momentous consequences for the course of history in the nineteenth century. It had a devastating effect on the already compromised marriage of the Imperial couple and interrupted the security inherent in the immediate line of Habsburg dynastic succession. As Rudolf had no son, the succession would pass to Franz Joseph's brother, Karl Ludwig and his issue, Archduke Franz Ferdinand. This destabilization endangered the growing reconciliation between the Austrian and the Hungarian factions of the empire, which became a catalyst of the developments that led to the assassination of the Archduke and his wife Sophie by Gavrilo Princip, a Yugoslav nationalist and ethnic Serb at Sarajevo in June 1914 and the subsequent drift into the First World War.

...
Wikipedia