On this page of The Quarry game guide, you will find information on how to rescue Nick, one of the main characters of the game.
Chapter 8. Nick for most of the game is transformed. You can't kill him at the very beginning, e.g. by taking the longer route to run to the wounded man in chapter 3. Nick may die at the hands of Laura as she takes aim at him in the basement of the Hackett home. If you want the man to survive, don't let her shoot.
Nick's transformation is impossible to avoid. This is one of the sequences that needs to happen in the game regardless of your decisions. A transformed Nick does not die unless Laura kills him. He can, however, kill Abigail and Jacob if you make those decisions. Their deaths are described on separate pages of our guide: