Which night was it that Fu Shenxing mentioned in the letter?

Answer 1

Fu Shenxing's letter that was in his hand referred to the night when Fu Shenxing had sex with He Yan. He Yan had made a condition to him, that was, if he could tell He Yan everything about her before they had sex, he would agree to it. However, Fu Shenxing didn't tell He Yan what she wanted him to say. Instead, he chose to have sex with She Yan, which eventually led to Fu Shenxing's death. Therefore, the night in the novel referred to the night when Fu Shenxing and He Yan had sex.