What mysteries remain at the end of the chapter 2?

The case of Mr. Hyde is full of speculation. After leaving this scene, Utterson goes to see Dr. Jekyll, but Poole, Jekyll's butler, reports that the doctor is not at home. From this conversation, Utterson gleans that Jekyll's house, around the corner from the mysterious door, is L-shaped, and that Hyde's mysterious door is actually an entrance to Jekyll's old dissecting room. Utterson also learns that Hyde never dines in the house, but visits often. After leaving Jekyll's home, Utterson walks home and decides that Hyde must be blackmailing Jekyll, perhaps for some terrible act he committed earlier in his life.