Vincent Braun and Karl Grünfeld are on a climbing tour that comes to an abrupt end when Karl loses his footing, falls into the ropes, and slams against the rock face. Dr. Martin Gruber hurries to their aid with his brother Hans and their colleagues of the mountain rescue service. Later, in the clinic, Gruber realizes that it was a blessing in disguise for Karl. It is Vincent who is giving more cause for concern. He has been suffering from a flu that causes strong circulatory problems for quite a while now. After several medical examinations, he is told by Dr. Gruber that it is not a flu, but a massive heart-valve defect that must be operated on urgently. This comes as a shock not only to Vincent’s best friend Karl, but also to Karl‘s sister Lena, who has secret feelings for Vincent.