In February 2012, in a Munich flat belonging to the elderly recluse, Cornelius Gurlitt, German customs authorities seized an astonishing hoard of more than 1,200 paintings, drawings and prints. When Hildebrand Gurlitt's trove became public in November 2013, it caused a worldwide media sensation. Catherine Hickley has delved into archives and conducted dozens of interviews to uncover the story behind the headlines.