What trigger strange story in book of the case dr. jekyll and mr. hyde chapter one?

In Robert Louis Stevenson's novella 'Strange Case of Dr Jekyll and Mr. Hyde', the initial triggering incident that sets off the story occurs when a mild-mannered and well-respected London doctor named Henry Jekyll accidentally encounters an unpleasant and degenerate figure named Edward Hyde. This encounter happens near Jekyll's home on a foggy evening.

Mr. Hyde tramples and injures a young girl in a reckless and malicious act. Dr. Jekyll witnesses the incident and feels compelled to intervene, offering financial compensation to the victim's family on Hyde's behalf. He manages to send Hyde away and assists the injured girl, ensuring that she receives proper care.

This encounter leaves Dr Jekyll deeply disturbed and intrigued by the profound evil he perceives in Mr. Hyde. it marks the beginning of his scientific exploration into the duality of human nature, leading him to conduct experiments that ultimately result in the creation of the sinister alter ego, Mr. Hyde.

From this initial incident, the narrative unfolds, delving into the unsettling consequences of Dr. Jekyll's experiments and exploring the moral and psychological complexities that arise from this strange and unsettling encounter.