The beginning of this story introduces us to the narrator. It is clear from the opening sentence that this is a man who has reached the end of his career, and he is somebody who has enjoyed a comfortable and successful existence without having had to work too hard. This is something he stresses, saying:
I am one of those unambitious lawyers who never addresses a jury, or in any way draws down public applause; but in the cool tranquillity of a snug retreat, do a smug business among rich men's bonds and mortgages and title-deeds.
Given what occurs later, we can understand how the case of Bartleby has stayed with him for so long. He describes the law office where he worked for so long, and his various employees before he employed Bartleby. However, the introduction makes it clear that Bartleby is the main focus of this tale:
But I waive the biographies of all other scriveners for a few passages in the life of Bartleby, who was a scrivener the strangest ever saw or heard of. While of other law-copysists I might write the complete life, of Bartleby nothing of that sort can be done... Bartleby was one of thos beings of whom nothing is ascertainable, except from the original sources, and in his case those are very small.
This story then is an attempt of its narrator to "ascertain" Bartleby as much as possible based on the scant evidence he has access to. The narrator of this story therefore begins this tale almost as if it were something of a mystery. He introduces those involved and then also introduces the central character, who he will present to us in his efforts to work out his significance.