Rainsford is and American who is both a world famous big game hunter and an author of a book detailing how to hunt snow leopards that are found in Tibet. As a hunter, he has been in "tight" places and faced many dangers. As an author, he has a keen intelligence and an appreciation for elevated conversation. He also enjoys the refined things of life that a renowned reputation and riches can provide a person.
Rainsford begins his unfortunate encounter with Zaroff when he hears shots in the distance and falls off a yacht and into the Caribbean Sea. Though Rainsford is a hunter, he is a moral man with well defined definitions of right and wrong. When he and Zaroff meet and converse, he is shocked at Zaroff's human hunting penchant and believes Zaroff to be a murderer. While Zaroff is hunting Rainsford, Rainsford uses all his prodigious knowledge of hunting and the hunt to outsmart Zaroff until at one point Zaroff outwits him.
While Zaroff plays with Rainsford as with a mouse, Rainsford is actually frightened. But in the end, Rainsford wins by capturing the hunter in his bedroom and slaying him there. We know that Rainsford is a moral man with elevated principles and knowledge of right and wrong, yet when Rainsford sleeps comfortably in Zaroff's bed at the end of the hunt that Rainsford has won, some argue that this may be an indication that Rainsford's experience has made him cross his own line and therefore will replace Zaroff as the hunter of men.