According to official records, Yongzheng died of a sudden illness in Yuanmingyuan. There were very few people present at that time, so the cause of death of Yongzheng recorded in the official history was not clear, so Yongzheng's headless body was a mystery from beginning to end. Because there is no official record, we can only look for some clues from folklore. This brings us to Lv Siniang who was persecuted by the literary inquisition. Lv Siniang is a combative person. He watched his family die at the hands of Yongzheng, so he was bent on revenge.
The first theory is that after Lv Siniang's family persecuted him again, he was lonely and helpless and had to wander around the world. In the process of wandering, when he met a master, he worshipped him as a teacher and learned the skill of climbing over eaves and walls. So I sneaked into the palace and killed Yongzheng when the night in the palace was the most relaxed. But there is no doubt about it. After all, it is the palace, which is heavily guarded. It shouldn't be that easy for a weak woman to assassinate the emperor.
The second theory is that Lv Siniang entered the palace as a nun and only moved her hand when she slept at night. As we all know, after Qianlong ascended the throne, a policy was implemented, that is, the concubines in the bedroom must take off their clothes in advance and be sent in by Mammy with a quilt. We have reason to believe that such a decision was definitely not made out of thin air, so it is likely that there were some bad cases during the Yongzheng period, so such a decision was made. But it is not clear how Lv Siniang left the palace with his head after killing Yongzheng.