All men are dogs

Today An Xiulan had to visit a penitentiary with her project partner to interview their client. Her case partner had been acting aloof for some reason. She didn't know what happened to Zhang Yiming to have him behave in such a manner but she tried to not let his attitude get on her nerves. 

"I will talk to the client while Miss An will take the notes, " Zhang Yiming said and An Xiulan agreed. As they entered the room where the client was sitting on the chair with his hands cuffed and they were two empty chairs for them too. 

They greeted the client who was arrested on the charges of murdering his wife. 

"Miss Cao, will you tell us what happened that day?" Zhang Yiming questioned. However, the client just stared at the wall blankly, not saying a word at all. 

Zhang Yiming asked the question again but Mr Cao didn't reply to him.