Task: Question Answering
Input (English): Passage: Tomas, a successful brain surgeon in Communist Czechoslovakia, is pursuing an affair with Sabina, an equally care-free artist in Prague. Dr Tomas takes a trip to a spa town for a specialized surgery. There, he meets dissatisfied waitress Tereza, who desires intellectual stimulation. She tracks him down in Prague and moves in with him, complicating Tomas's affairs.
Tomas asks Sabina to help Tereza find work as a photographer. Tereza is fascinated and jealous as she grasps that Sabina and Tomas are lovers, but feels affection for Sabina. Nevertheless, Tomas marries Tereza, in a simple ceremony with both perpetually laughing, followed by her double standard distress about Tomas' promiscuity. Although she considers leaving Tomas, she becomes more attached to Tomas when the Soviet Army invades Czechoslovakia. Amidst the confusion, Tereza photographs demonstrations against the Soviet forces, then hands the rolls of film to foreigners to smuggle to the West. Facing the stultifying reality that replaced the Prague Spring, Tomas, Sabina and Tereza flee Czechoslovakia for Switzerland: first Sabina, then the hesitant Tomas and Tereza.
In Geneva, Sabina encounters Franz, a married university professor: they begin a love affair. After some time, he decides to abandon his wife and family for her. After hearing the declaration, Sabina abandons Franz, feeling he would emotionally weigh her down. Meanwhile, Tereza and Tomas attempt to adapt to Switzerland, whose people Tereza finds inhospitable. When she discovers that Tomas continues womanizing, she leaves him and returns to Czechoslovakia. Upset by her leaving, Tomas follows Tereza to Czechoslovakia, where his passport is confiscated, trapping him in-country: nevertheless, his return elates Tereza. They are re-united. 
Question: What is the name of the person that caused Franz to leave his family?
Output (English): Sabina.