The tall stranger keeps inviting Tereza to his flat. She knows nothing about him except that he is an engineer, and by the third invitation, she accepts. Tomas has always told her that love and sex are two different things, so she decides to test his theory. She thinks that she wouldn’t stay for very long. She would have a cup of coffee and stand on the very edge of infidelity without looking over. Then, when it came time for sex, she would say: “It wasn’t my choice.” And then he would say that he didn’t have any right.
Again, Tereza does not want to be unfaithful to Tomas. She takes their love seriously, and she can’t separate sex from romantic attachments and heavy feelings. In this way, it isn’t Tereza’s choice; rather, she is forced by Tomas, in a way, to test his theory about love and sex. Still, she sees infidelity—both Tomas’s and her own—as a sort of death of their love, hence the executioner on Petrin Hill and the tall stranger’s association with him.