The “UFO abduction” scenario changed significantly after the publication of Hopkin’s book Missing Time in 1981. Prior to that time, UFO abductions were supposed to occur only when people ventured out to lonely, deserted places late at night, and encountered aliens (Betty and Barney Hill, Travis Walton). Hopkins’ contribution was to entirely sever the connection between UFO sightings and UFO abductions.

To explain why nobody ever sees or photographs somebody else being abducted, Hopkins suggested that the aliens have the ability to make themselves, and their abductees, invisible during this process.