Episode 16 recap: Gu Yuan went undercover in the Tong Mansion to investigate the death of Li Hua.

Early in the morning, Yan Jun Jie startled Gu Yuan and his team, who were engrossed in their investigation, by wearing a ghost mask he had bought. Just then, they received a notification that a family member had died of a heart attack and that a forensic examination was required to obtain a death certificate. Initially, Che Su Wei had other matters at hand and wanted Ren Meng Yao to handle it. However, upon learning that it was related to the Tong family, she realized it might be Li Hua and hurriedly rushed to the Tong Mansion.

To Che Su Wei's surprise, the deceased person turned out to be Li Hua, who had died of a heart attack. Although she was saddened by the news, she had to conduct an autopsy on Li Hua's body. Che Su Wei conducted a preliminary examination of Li Hua's body and then inquired about the whereabouts of Tong Jiu Long, only to find out that he hadn't returned yet.

Che Su Wei believed there was something suspicious about Li Hua's death because there was an extra pill in her medicine bottle. Li Hua had a habit of taking her medication and would not forget to do so. Therefore, Li Hua's death must have been intentionally arranged by someone. Gu Yuan comforted the distraught Che Su Wei and decided to help her investigate the cause of Li Hua's death.

The local police summoned everyone in the Tong household for questioning but found nothing suspicious. They only discovered that Tong Jiu Long had a secret relationship with the maid Cui Ping, but nothing else. Che Su Wei asked Tong Jiu Long about the divorce lawsuit, to which he responded that he hadn't received any divorce agreement from Li Hua. He also claimed to be very busy and had no time to argue or quarrel with Li Hua, which could affect their marital relationship.

Tong Jiu Long had an alibi; at the time of the incident, he was on a train from Hangzhou to Shanghai and had a train ticket and passenger proof. The local police had not found any suspicious evidence against him. As there was no evidence of homicide in Li Hua's death, Gu Yuan thought it was time for Che Su Wei to close the case. However, Che Su Wei shared the tragic fate of Li Hua with Gu Yuan, emphasizing that Li Hua was a pitiful person and that if they didn't uncover the truth for her, no one else would.

After listening to Che Su Wei, Gu Yuan decided to help her with further investigation. As luck would have it, he could participate in the investigation without being recognized by the Tong family because they didn't know him. Therefore, Gu Yuan decided to go undercover in the Tong Mansion. He posed as a household servant and secretly inquired about Li Hua's death. Coincidentally, there was a disagreement between the cook, Wang Tiezhu, and Cui Ping, and Wang Tiezhu borrowed Gu Yuan to use in the kitchen, giving Gu Yuan an opportunity to intervene.

Cui Ping acted like the mistress of the Tong family and bossed around all the servants. She made them resentful but afraid to voice their complaints. Unhappily, Wang Tiezhu prepared a few dishes for Cui Ping, and Gu Yuan intentionally added extra salt. When Cui Ping tasted the food and became extremely angry, she stormed out, carrying the dishes, to settle the score in the kitchen.

After Cui Ping left, Gu Yuan went to her room to investigate. He inadvertently saw Cui Ping wearing a mask and a black cloak, and he secretly followed her. It was then that he discovered that the Tong family was controlled by an organization that worshipped the Yongchang family god. While Gu Yuan was spying, he noticed that Tong Jiu Long was also peering outside the window, which made him even more suspicious of this organization.

Gu Yuan returned to the police station to inform Che Su Wei and the others about the situation in the Tong household. He wanted to start with Wang Tiezhu and uncover the truth behind the Yongchang family god. Gu Yuan brought something valuable back to the Tong mansion and engaged in in-depth conversation with Wang Tiezhu. When Wang Tiezhu became suspicious about the missing items in the kitchen, Gu Yuan lied and claimed that Xiao Liang had stolen them.

Upon learning about Xiao Liang's actions, Wang Tiezhu wanted to communicate with the Yongchang family god to have him punish Xiao Liang. Gu Yuan expressed his desire to learn cooking from Wang Tiezhu, and Cui Ping wanted to take him to meet the Yongchang family god, but he didn't agree. Gu Yuan successfully fooled Wang Tiezhu and gained his trust, so Wang Tiezhu decided to have a drink with Gu Yuan in the evening.

As agreed, Gu Yuan met Wang Tiezhu and poured him a lot of alcohol. When Wang Tiezhu became drunk, Gu Yuan questioned him about the Yongchang family god. After Wang Tiezhu was heavily intoxicated, Gu Yuan took him outside, and that's when Yan Jun Jie appeared wearing the mask he had bought before, pretending to be the Yongchang family god.

Gu Yuan and Yan Jun Jie staged a performance, startling Wang Tiezhu as if he had encountered a ghost. Yan Jun Jie used divine powers to punish Gu Yuan, slapping him across the face from a distance, making Wang Tiezhu believe that he was indeed the Yongchang family god.

Although Wang Tiezhu had some suspicions initially, Yan Jun Jie managed to deceive him with a few words. Eventually, Wang Tiezhu sent a message to the Yongchang family god, asking him to reveal the identities of the wrongdoers in the Tong family. After learning about the message being sent, Gu Yuan realized that Xiao Liang was in trouble, so he had Wang Tiezhu taken back to the police station while he rushed to save Xiao Liang.

When Gu Yuan arrived at Xiao Liang's room, he found that the person had already been taken away, but the bed was still warm, indicating that they had just left. He immediately set out to track and rescue the person. Gu Yuan arrived in time to save Xiao Liang, but the servants who were planning to bury Xiao Liang alive took the opportunity to escape. After they fled, Gu Yuan discovered that there were other bodies in that pit.