The mood right from the beginning is ominous. There is an element of mystery, curiosity, and danger. This comes out nicely, for example, in the words of Whitney, when he speaks of the mysterious island called, "Ship-Trap." He says:
"The old charts call it `Ship-Trap Island,"' Whitney replied." A suggestive name, isn't it? Sailors have a curious dread of the place. I don't know why. Some superstition--"
What makes the mood even more fearful and mysterious is that the island is supposed to be so frightening of a place that experienced sailors don't even want anything to do with it. Here is a quote that shows the great fear of the men, even the toughest of them. Whitney says:
"Yes, even that tough-minded old Swede, who'd go up to the devil himself and ask him for a light. Those fishy blue eyes held a look I never saw there before. All I could get out of him was `This place has an evil name among seafaring men, sir.'
When Rainsford hears gun shots in the distance, the mysterious element becomes even stronger. What could be there?
Finally, when Rainsford swims to the shore and meets Ivan and general Zaroff, the worst is confirmed. The two hunt humans for sport and Rainsford is their next prey.