The first person that arrives at the crime scene is known as first responder. A first responder is a trained personnel that responds or arrives first at the crime scene. The duty of a first responder is to protect the people and the crime scene and also to regulate the changes that affected the crime scene.
It advances the plot because the conversations that they have foreshadow what is going to happen in the cellar. ex-montresor gave fortunato more and more wine