Poul Anderson 
Devil’s Game [EPUB ebook] 

On an isolated island, seven people with a desperate need for money play a game conceived by an intelligence of perfect evil. The rules are simple: each player will perform an act: each of the others must duplicate it, or be eliminated. All that the players have in common is their desperation. One is a mercenary soldier with a taste for proving his manhood through self-torture. Another is a porno-starlet. A third is a perfectly ordinary mother whose seven-year-old’s life depends on a million-dollar medical treatment. Each of the seven thinks he or she will do anything; all but one of them are wrong.