Lonely People Kill

Su Ziqiu, a woman from Hong'an County, failed to return after receiving a call and went out. The next day, the police found that she had fallen off a cliff. After understanding, she had no motive to commit suicide, and this incident was not as simple as falling off a cliff in a car accident. What kind of behind-the-scenes killer is able to surround the police? What kind of darkness is in the heart that leads to the occurrence of this case? What kind of trust needs to be gained to make this method successful? This is definitely not an ordinary murder case, or it has been planned for a long time...