Sanger Rainsford thinks he has found a safe haven when he finds himself in General Zaroff's beautiful and civilized mansion in "The Most Dangerous Game" by Richard Connell. He fell off his ship and managed to swim to this island, and he was afraid it was uninhabited, though he did hear shots and animal-like cries. Now he is here and thinks this is more than he could have hoped to find in such a place. 

It is true that the man who answered the door, Ivan, is a bit terrifying, but General Zaroff is a delightful and civilized man in every way--and he is an accomplished hunter. It really is the best place Rainsford could have been, he thinks. After a delightful dinner, he and Zaroff begin to talk about hunting, and the general reveals that he has grown bored with hunting animals because they do not have the ability to reason. In a slow, calm way, Zaroff reveals that he now hunts humans. 

Rainsford is appalled at the horrifying revelation, and he is even more appalled when his host makes this offer:

"And now," said the general, "I want to show you my new collection of heads. Will you come with me to the library?"

"I hope," said Rainsford, "that you will excuse me tonight, General Zaroff. I'm really not feeling well."

Obviously what Zaroff is calmly offering to show his guest is the mounted heads of the men he has been hunting; just the thought of it sickens Rainsford, and he makes his excuse not to see the horrific sight. He tells the general he is not feeling well, and that is undoubtedly true. Rainsford is sickened at the thought of something we would all, I hope, find grotesque and appalling, and he has no intention of viewing General Zaroff's awful collection of human heads.