Who was it?

On a Monday night, Mary was sleeping peacefully and she heard a knock on the door. It was her husband. He had came back from his official tour. She served him dinner and both of them went to bed. The next day early in the morning Mary again heard a knock on the door. She went to open the door and saw her husband standing there. She ran towards her bedroom and there was no one. She was shocked and confused. She thought that she had saw a dream but just to be sure she went to check the CCTV camera.

She saw that she went to open the door at night and a man disguised as her husband came in. She told her husband about the incident and they reported to the police. Police came and investigated but found no clues except for the cctv footage. 

Police called Mary and asked if she had any suspects in mind. She refused as she could not think of any person who could do such a suspicious thing. On that evening Mary received a message from an untraceable number which had some personal photos of her with a message "Stop the investigation or else I'll leak them". She told her husband and he told her that she should stop the investigation as her photos getting leaked could be insulting. Mary did not want to stop the investigation and met the investigating officer when her husband was in his office and she told the officer everything and requested him to do a secret investigation. The officer understood her situation and agreed. 

After a few weeks the police found prime suspects. They were her brother Jack, her neighbour Trent and her ex boyfriend Ben. Jack was constantly trying to convince her sister to stop the investigation. Trent was stalking her and had a crush on her. Ben was trying to win her back by sending her creepy texts. 

Mary was asked that who she thinks could do it. She said Ben as he was doing creepy things. 

Her husband again went for an official tour and police told Mary that they got a tip from one of their man that the culprit is going to come to her house again today. She was told that police in civilian get up would stay around her house. 

At 11:30PM Mary heard a knock and went to open the door she saw the same man with a envelope in his hand. He came inside her house and after a minute police came too. And arrested him. In the envelope he had brought photos of Mary to blackmail her. 

When police investigated him they came to know that he was Mary's husband's twin and Mary's husband asked him to blackmail her and leak her photos so he could get a opportunity to divorce her because he was having an affair with her best friend Julie. Mary's husband and Julie were asked to report to the police station immediately. They were investigated and Julie accepted that she had an affair with her best friend's husband but he refused it. Mary was heartbroken. The three (Julie, Mary's husband and his twin) were sentenced to prison. Julie and Harry (husband's twin) later got a bail. 

One day Mary's husband demanded to talk to the investigation officer. And after somedays police went to Mary's house with a search warrant. They found her with Harry and found some letters and took both of them in remand. 

Mary confessed that she did all this because she loved Harry and wanted to get rid of her husband. She planned it all with Harry and Julie. Her husband knew that and he himself told the police officer because he had seen his wife with his brother but did not take any actions because he loved her immensely and did not want to loose her.