De Mayerling à Sarajevo is the story of Franz Ferdinand, heir to the Austria-Hungarian empire, who falls in love with Sophie Chotek, a Czech countess. He's already a problem to the Crown because of his political ideas; this love affair with someone not of royal blood, further breeches the protocol.
The Crown allows this union only after the couple agrees to a morganatic marriage. The emperor further neutralizes Franz by making him inspector general of the army, and sending him afield for months at a stretch. In the June of 1914, fearing for his safety, Sophie seeks permission to accompany Franz to Sarajevo. The royal protocol dictates that no army troops should attend Franz while she is present. An assassin strikes, killing both Ferdinand and Sophie. There death becomes the trigger point of World War I.