Doctor Liu/Spoilers

History
Doctor Liu has been working with the Bai family by giving the medication to make Bai Ruo Li sick every time the Empress Dowager asks her to visit.

Peach Blossom Banquet
The Doctor arrives after hearing a young girls has started to bleed out; he doesn't see who it is as thier face is covered. He misdiagnoses her with a "joyous pulse" - meaning she is pregnant - as he was paid to do by the Wu Wei Manor's Madam.

Bai Ruo Qi must prove her innocence and so she throws the Court Doctor Liu under the bus in front of the Empress Dowager. Empress Shu - who was there for the fun of watching Bai Ruo Li fall from grace and also Bai Ruo Qi's Aunt - assists Bai Ruo Qi. Doctor Liu is almost immediately thrown in jail. However, Bai Ruo Li asks the Empress Dowager to get to the bottom of this and thus Bai Ruo Lii is able to interrogate Doctor Liu. He retaliates for being discarded by revealing that every time Bai Ruo Li was invited to the palace, the Bai family would get medicine from him to make Bai Ruo Li sick. He also divulges that he supplied medicine so that Bai Ruo Qi could have Bai Ruo Li raped by an extremely ugly young man.