Out in a deserted desert world sits Westworld; part of the most realistic amusement park on the planet for adults. The place is called Delos, and it consists of three separate words: West World, which is modeled off the American Southwest of the 1800s, Medieval World, which is modeled off old Europe ca. 1000AD, and Roman World, which is modeled off ancient Rome. At Delos, you can do what ever you want to do, and be whomever you want to be for $1000 a day.
Everything in these worlds is perfectly recreated down to the most minute detail, and the robots that interact with the guests are so realistic, the only way to tell them apart from humans is by their hands.
As Peter and John arrive in West World, Peter feels silly acting like a cowboy. John has been there before, and he shows Peter around. While the two talk in a saloon, a Gunslinger bumps into Peter, and Peter kills the robot in self defense.
While everything seems to be fun and games, the scientists running the robots, begin to notice striking abnormalities in their creations. They are having system failures at an alarming rate, and the problem is spreading from robot to robot like a disease. Eventually, Delos loses control of the robots, and all hell breaks loose.
John is killed in front of Peter by the Gunslinger, and he is forced to run for his life from the Gunslinger. Across each world, the robots are killing all the guests while the Gunslinger pursues Peter with a vengeful vendetta. Finally, Peter is able to get the better of the robot in Delos’ labs by throwing acid in its face. He then runs off into Medieval World where he sets the Gunslinger on fire.
As Peter sits alone in a dungeon, he is shown as the sole survivor of Delos. All the robots now sit in a deathly silence of their own with their batteries drained.