Actor, Screenwriter and Film Producer. Kastner was one of the most popular leading men in silent films during the 1910s and 1920s. After a short, seventeen-day stint in the military before being relieved of his duties due to an injury, he travelled to Berlin and took acting lessons then relocated to Hamburg where he performed at the Harburger Theater. He made his film debut in 1914 in the comedy short 'Engelein' (Little Angel) and followed the success of that film with the sequel 'Engeleins Hochzeit' (Little Angel's Wedding) in 1916. Kastner quickly became a matinee idol and cemented his romantic image by appearing as the ardent suitor to popular actress Dorrit Weixler in a number of films. In 1921, he was voted "The Best German Actor" and that year appeared in 'Der Silberkönig' (The Silver King) opposite leading lady Ossi Oswalda, and the following year, founded his own film company. Other popular films he appeared in were 'Hilde Warren und der Tod' (1917), 'Das Herz des Casanova' (1919) and 'Das Paradies im Schnee' (1924). Kastner wrote the screenplays for four films that he would produce and star in: 'Nur ein Diener', 'Das Herz des Casanova', 'Der letzte Sonnensohn' and 'Der Weltmeister', all released in 1919. His career was almost cut short in 1924 when he was involved in a serious motorcycle accident in Switzerland, which left him with injuries from which he never fully recovered. After a year of rest and recuperation, he returned to the screen in 1925, however by the late 1920s his career began to falter since he was no longer able to play the young, seductive types which had made him famous and his roles in films grew smaller, although he still had a measure of success in such films as 'Die Brüder Schellenberg' (1926) and 'Der Orlow' (1927). The onset of sound films proved disastrous to Kastner's career in 1930 upon the release of his first talkie titled 'Das Land des Lächelns' (The Land of Smiles) when filmgoers discovered that he stammered. He would go on to make one more film, 1930's unsuccessful 'Tingel-Tangel'. After failing to garner any more roles because of his speech impediment, he began to suffer from depression and spent the next two years struggling to regain his public popularity but to no avail. Kastner, who was married to German actress Ida Wust from 1918 to 1924, rented a room in a small hotel and commited suicide by hanging himself.