What is the reason that the stranger gives Mrs. Hall for his sudden arrival?

In the first chapter of the novel, the stranger introduces himself to Mrs. Hall and exhibits some peculiarities which take her by surprise, such as his refusal to let her take his hat to be dried. She notices that he is covered in bandages and assumes that he has had some kind of accident or operation which means he doesn't want to show his face. However, she is unable to solicit any information out of him on this score, and he does not, at this point, offer any explanation as to why he is there.
In the second chapter of the book, however, the stranger apologizes for his abruptness and says that he is "an experimental investigator." The cases which he would like to have sent for are, he says, delicate and contain the instruments of his trade. He says that he has come to stay in Mrs. Hall's establishment because of "a desire for solitude." He does not want to be disturbed while he is working, and, moreover, he tells Mrs. Hall that "an accident" has given him certain peculiarities. He says he has weak eyes, which mean he sometimes needs to be locked in a dark room for a time, and that noise annoys him.