In the near future, a high-tech amusement park called Delos offers guests a unique vacation experience. The park is divided into three themed "worlds" — West World, Medieval World, and Roman World — each inhabited by lifelike androids designed to fulfill visitors' wildest fantasies. For a hefty sum, patrons can immerse themselves in an authentic re-creation of the selected time period, complete with elaborate costumes, settings, and the chance to live out adventures without any real-world consequences.

Two friends, Peter and John, choose West World, where they can live out the quintessential western experience as gunslingers and heroes in a lawless land. As they delve deeper into their roles, initially enjoying bar brawls, brothel visits, and a simulated gunfight with a robotic gunslinger, they notice odd malfunctions beginning to affect the androids. While the guests are initially unconcerned, believing their safety is guaranteed by the park's technology, these glitches hint at a looming crisis that threatens to shatter the illusion of control and turn the ultimate fantasy vacation into a nightmare.