Short Answer 
Dr. Lanyon receives a mysterious letter from Dr. Jekyll with strange instructions to retrieve items for Mr. Hyde at midnight, raising suspense and curiosity. Ultimately, Lanyon experiences a shocking revelation that Jekyll and Hyde are the same person, emphasizing the theme of duality in human nature.
Step 1: Receiving the Mysterious Letter
Dr. Lanyon receives a mysterious letter from his old friend Dr. Jekyll. In the letter, Jekyll provides strange instructions that set the stage for the unfolding events. He requests that Lanyon procure specific items from a cabinet, which adds an air of urgency and intrigue to the situation.
Step 2: The Unusual Task
Following Jekyll’s instructions, Dr. Lanyon is to retrieve the items and deliver them to Mr. Hyde at his home. This task is to take place at midnight, heightening the suspense and creating an atmosphere of mystery. The nature of this request raises questions about the relationship between Jekyll and Hyde, leaving Lanyon in a state of confusion and curiosity.
Step 3: The Shocking Revelation
Upon completing the task, Dr. Lanyon experiences a shocking revelation‚ÄöAihe discovers that Dr. Jekyll and Mr. Hyde are, in fact, the same person. This realization is not only a twist for Lanyon but also adds to the perplexity of the readers. It deepens the overarching theme of duality and the complexities of human nature within the narrative.