From love's joy and love's sorrow, maternal love and partner love, self-love, love-hate, and "forbidden" love - prominent examples lead researcher Dietmar Grieser to explore the question: What defines love? What can we learn from the relationship happiness, but also from the relationship conflicts of others? The 16-year-old Beethoven loses his best friend with the death of his mother; heir Franz Ferdinand even stands up to the emperor regarding his choice of bride; and what does the creation of the US cult film "Casablanca" have to do with a mysterious honeymoon trip to Vienna in 1938? We get to know "mass murderer" Agatha Christie as a devoted wife, and Erich Kästner as a pampered mama's boy. Anyone interested in complicated partnerships cannot overlook Franz Kafka and Bertolt Brecht, Benjamin Britten and Richard Gerstl.