After the death of his wife, chemist Professor Helmerding lives only for his work and his two children, Sabine und Thomas. Then he suddenly becomes acquainted with the laboratory assistant Barbara Rohn. He falls in love with her and they marry. Barbara is happy to leave her job and no longer to be exposed to the advances of her colleague Dr. Deinert. He gives Helmerding's daughter, Sabine tennis lessons and Barbara soon learns of an affair between him and Sabine. When Barbara visits Dr. Deinert in order to confront him, rumours are rife about an affair between Barbara and Dr. Deinert. In order to protect Sabine she discloses nothing of Sabine's conduct to Helmerding. Sabine soon realizes how greatly Barbara trusts her. But Thomas, Helmerding's son, is tired of the gossip concerning his stepmother's supposed affair with Dr. Deinert and he confronts the latter – with a loaded gun.