In the third episode of Princess Zhu Huan, Dong Er got smallpox in heaven and earth. Which episode is it?

This is part of the plot.

Yongqi was at a loss in the new house.

In the bachelor's office, Fallon and Fujin are in Dong Er's room, and the doctor too much is diagnosing Dong Er. Wei Zi hurried into the room and asked. After consultation with too many doctors, Dong Er was diagnosed with smallpox. Wei Zi couldn't believe that smallpox caused huge casualties in the previous dynasty, and once infected, it was almost incurable. The sudden blow made Wei Zi and Er Kang unbearable. This disease is caused by.