In the story of Lock the Door, Fang Hui rents a house and lives alone. On this day, she was reading in the room. She heard the lock when she opened the door. She hurried to the door, and the sound of pressing the password came clearly from her door. Maybe someone is doing an experiment outside, and there are two hints that he made a mistake. Fang Hui went to the security guard to check the monitoring, and the security guard told her that the monitoring was not good. She had to give up. The next day, at work, she met a real estate agent. Her house hasn't expired yet, but the agent has repeatedly urged her to move out. She refused to agree.

One day, she was taking a bath at home when she suddenly heard the sound of unlocking the password lock outside the door. She crept to the door, and sure enough, she heard someone trying to open her password lock again. The man shook her door outside the door after failing the test several times. She held her breath and picked up something to protect herself.

One day, she swept the floor with a circular robot after work. As a result, her mopping robot ran under the bed and she took it out with her hand. As a result, she accidentally found a body under the bed. She screamed with fear and called the police.

When the police arrived, they saw many men's clothes and slippers in her room. She said that she lived alone and put those men's clothes and shoes in order to create the illusion that there were men in the room.

Because she is alone in the field, the boss wants to bully her even more unscrupulously, and the "black-hearted" real estate agent also intends to do something bad to her. However, these two people died suddenly and strangely. At the same time, her best friend disappeared for no reason. Later, her body was found at the seaside, and her best friend was brutally dismembered by the murderer.

In the end, the truth of the case came out. The murderer is a person who no one expected. He is a gentle vet, Zheng Fei. Zheng Fei grew up with his grandfather. Desperate for love, he firmly believes that there will be a gentle girl in his life. That day, when Fang Hui and Xiaoman brought a stray cat to him for treatment, he thought he had found the love of his life. He fell in love with Fang Hui.

He didn't expect to find love through normal channels. He went to extremes. He wanted to care about Fang Hui all the time, so he sneaked into Fang Hui's home and installed a surveillance camera under the air conditioner. So he can see her all the time. Later, the real estate agent tried to unlock Fang Hui's room twice, and Fang Hui's boss, Mr. Li, tried to molest Fang Hui, which was clearly seen by him in the monitoring. So he made a decisive move, first solved the real estate agent, and then kicked Li downstairs.