Zhai Hua was at Zhai Sheng's office when she found out about Wei De. She also used the telephone at Zhai Sheng's office to make a phone call to Qiao Nan.
Since the information might be with Zhai Hua, Zhai Sheng had to think of the worst-case scenario—Zhai Hua had read the information.
He was not worried that Zhai Hua might not believe the information. On the contrary, he was worried that she believed it and would act rashly.
Zhai Sheng kept calling Qiao Nan along the way, trying to contact her.
With regard to Wei De, Zhai Hua refused to listen to anyone except Qiao Nan.
Therefore, Zhai Sheng wanted to contact Qiao Nan to remind her to stall for time.
