At the end of Chapter 1, Stevenson suggests that Utterson knows more about Enfield's story than he is willing to admit. Remember that one of Utterson's qualities is his ability to keep strict confidences and remain always an honorable gentleman, even when indiscretion (such as opening Lanyon's letter prematurely) seems wise.
Now, in Chapter 2, we are given Utterson's own private narration, in which we discover that he is not only a close friend to Dr. Henry Jekyll, but he is also the executor of Jekyll's will. Thus, when Utterson returns once again to Jekyll's strange will and finds that all of his property under any circumstance is to be left to Edward Hyde, we now realize why Utterson was so fascinated with Enfield's narration.
In the first Chapter, we were only distantly involved with Hyde. But now that we know that Hyde will be the sole inheritor of Dr. Jekyll's large estate, and as Utterson's fears increase, so do ours. In such a mystery story, the reader is expected to wonder about the possibility of Hyde's blackmailing Dr. Jekyll. Since we trust Utterson, who has a great fear for Jekyll, our own fears are also heightened.
When Utterson visits Hastie Lanyon, who was once Jekyll's closest friend (along with Utterson), and we hear that Lanyon has not seen Jekyll since Jekyll first advanced some very strange and "unscientific" theories, we then have our first hint that the mysterious Dr. Jekyll is involved in some sort of unacceptable or advanced medical practice — at least from the viewpoint of such a traditionalist as Lanyon. The exact nature of Jekyll's practice will not be revealed until the final Chapter.
