Suspense is first built by foreboding. Something suggests an imminent conflict or life-threatening situation.
When Rainford and his friend are on a yacht, the Swedish captain mentions an eerie feeling he gets whenever he goes by a certain island. Sea lore tells of wrecked ships and sailors lost at sea. Later that night, Rainford hears gunshots from that direction and ends up falling overboard. He has no other choice but to swim to the island. He hears more shots, a piercing scream. He finds evidence of a hunt with much blood.
When R. finally finds human habitation, it is a Gothic-like castle perched on a high cliff with a gorgoyle-like door-knocker. He is first received by a butler (rather a henchman) named Ivan, a deaf brute pointing a pistol at him. Zaroff then approaches, excuses for such a poor reception. Although highly cultivated, he is swarthy with piercing eyes and pointed teeth. He also has a strange way of studying Rainsford, which makes him uneasy.
Zarkoff is flattered to receive Rainsford since they both share the passion of big game hunting. When R. realizes that Zarkoff hunts men as prey, he understands too late (after the reader!) that he too will be Zarkoff's "game." The fact that no one has ever "won" against Zaroff is no comfort; he must pit his wits against Zarkoff's in order to survive.
Who will win? Only the last sentence tells us. Periodic effect also creates suspense by witholding critical information until the very end.