Two gunshots echoed from Mayerling hunting lodge in the early hours of 30 January 1889, sending shockwaves through the Austro-Hungarian Monarchy. Crown Prince Rudolf was found dead alongside Baroness Mary Vetsera, his 17-year-old mistress. Mary had been shot by Rudolf, who, several hours later, turned the gun on himself. A scandal ensued, and the imperial family sought to erase all memory of the baroness’ presence at Mayerling. Countless theories have circulated since: murder by foreign agents or on the command of Rudolf’s hated uncle, Archduke Albrecht; an orgy gone wrong; a botched abortion; an assassination by a jealous neighbour. But what really happened on that fateful night that accelerated the onset of the First World War and the fall of the monarchy?