Why does poole contact utterson in Chapter 6 of Dr. Jekyll and Mr. Hyde?

In "Dr. Jekyll and Mr. Hyde," Mr. Poole contacts Mr. Utterson in Chapter 5, not Chapter 6. Poole, a servant in Dr. Jekyll's household, writes a letter to Utterson out of concern for Jekyll's well-being. He expresses worry about the doctor's health, his changed demeanor, and the strange occurrences in the laboratory. Poole fears for Jekyll's safety and requests that Utterson come to the house immediately to assist him in ensuring Jekyll's welfare.