While Europe and the United States dominate the art scene after World War II, Mark Rothko and Hans Hartung forged a discreet, friendly and very fertile bond. This documentary introduces the discovery of this little known and fascinating complicity between both artists. On the one hand, Mark Rothko, "the most violent of American painters" in his own words; on the other, Hans Hartung, a brilliant experimenter and "boxer" in front of the canvas. From the moment they met in 1950 in Hans Hartung's studio, there was a collaboration between them that resulted in huge, metaphysical and cataclysmic paintings. Then, Rothko gave a "lesson" to his European colleague, Hartung visited and paid homage to his elder and then mourned his suicide from Antibes, where he had a huge villa-studio built and kept the secrets of his relationship. This Rothko-Hartung encounter is an unprecedented and yet essential subject to understand a part of 20th century art.