In the 1930s and 40s, Martin Heidegger was arguably the world's most important and influential philosopher having won global recognition with this celebrated Being and Time in 1927. Heidegger was also wildly controversial having embraced Nazism in 1933, though he often clashed with the party's leadership. In 1942, Heidegger delivered a series of lectures in which he analyzed at length the poem The Ister, an ode to the Danube River written in the late 18th century by the German author Friedrich Holderlin. Rather than a simple celebration of verse, Heidegger's talks used The Ister as a jumping-off point for discussions of technology, cultural identity, political change, and the war which then gripped both Germany and the world. Authors, filmmakers, and David Barison and Daniel Ross examine Heidegger's work and his take on Holderlin's poetry as they travel the length of the Danube with cameras in this documentary. The Ister explores how many of Heidegger's notions have retained currency as the filmmakers interview Jean-Luc Nancy, Philippe Lacoue-Labarthe, Bernard Stiegler, and Hans-Jürgen Syberberg.