Initially, Yin Xun suspected that Si Fan had hired someone to inject drugs into Dai Ning's body. However, now that she thought about it, the probability of that was not very high.
If it was really Si Fan behind it, then he must have sent someone to monitor Yin Mo's situation at all times. That way, he would have already known about Yin Mo's imprisonment.
However, it was clear that he had no idea that Yin Mo was in prison because he had asked someone to look for news on her.
At that time, there was only Lin Zhu and her at the scene. When the police took Yin Mo away, they used the chairman's private passageway, so the other employees in the company building did not know about this.
Si Fan would never expect that she would really send Yin Mo to prison. He would probably think that Yin Mo was just locked up in the Yin family home again.