Why did Whitney tell rainsford about ship-trap island

From a narrative perspective, this sets up the suspense and conflict of the story. When Rainsford asks Whitney about the rumors surrounding the mysterious island, Whitney explains that the island simply radiates evil—even the captain and the crew of the boat were on edge as the boat approached the island.

The captain had told Whitney that he felt a profound sense of dread on passing through the waters that surrounded the island. Rainsford thinks that the captain is simply being overdramatic. Whitney surmises that perhaps this is the case of one sailor’s scary tale rubbing off on the whole crew. He explains to Rainsford that even though that might be the case, there is still something to be said for the ability of evil to be perceived, especially by those who face danger constantly.