An extraterrestrial mistake, a controlled space warp left open a fraction too long, a Wyoming hiker unknowingly walks into another world.
Alien explorers are studying Earth, moving to and from their planet through a controlled space warp exiting into the Wyoming wilderness. Mark Carter inadvertently enters the warp and is propelled to their world. His surprised hosts resent the intrusion.
While awaiting a decision on what to do with him, Mark is introduced to an "experience-sharing" machine, a form of virtual reality that captures snatches of alien life then permits others to live them as if first hand. But unknown to the aliens, the process stimulates Mark's mind. He learns to communicate mentally, manipulate objects remotely, even rearrange his DNA to imitate other creatures.
Mark's lover, thinking Mark is lost, travels to Wyoming and there goads the authorities into a search. Because the aliens are simultaneously attempting to learn about Mark's life on Earth, her involvement steadily deepens.