Evidence vs Speculation

XuXu is taken hostage by Yang Yu but Ji Bai is able to save her. During interrogation of Yang Yu, the kidnapper, Xu Xu determines that he was determined to kill Shiyong anyway. Attempting to convince Ji Bai of her theories, Xu Xu becomes exasperated. Ji Bai demands evidence and not just speculation, instructs her in correct investigative procedures, finds fault with her assumptions and admonishes her.