Bertha saw that he was lying but still so serious, she was very confused.

He's injured but still wants to hide it?

Did he think that if she knew he was injured, she would not only show no mercy but also sprinkle salt on his sore spot?

Yes, if Bertha angers her, she can't guarantee she won't do it.

If Derek didn't want to talk, Bertha didn't ask anymore, she turned around and went straight upstairs.

While passing by the medicine cabinet located on the wall ...