Dexter told Delilah that he has been studying German all week because the German visitors are coming today, but German is hard and all this studying has exhausted him. He also has been doing some extra grooming so that he will look really good when they come.
Dexter told Delilah that he would help her with her grooming as well. He wants to be sure she looks her best for the visitors. Delilah wasn't too happy with the advice because she doesn't like visitors and plans to stay well hidden while they are here.
Dexter told her she had to be clean anyway and gave her a vigorous bath which she didn't like very much.